A  PLAN 
FOR  COOPERATIVE  RESEARCH 
ON  THE  SALT  REQUIREMENTS 

OF 

REPRESENTATIVE  AGRICULTURAL 
PLANTS 

Prepared  for  a  Special  Committee 

OF  THE 

Division  of  Biology  and  Agriculture 

OF  THE 

National  Research  Council 


EDITED   BY 

BURTON  E.  LIVINGSTON 

DR.  A.  G.  McCALL, 

LABORATORY  FOR  SOIL  INVESTIGATIONS, 

un;v?=f?s!ty  of  M^RVLANP, 

, .  M  t'GE  PARK.   MD. 


SECOND    EDITION 

BALTIMOKB 
1919 


A  PLAN 
FOR  COOPERATIVE  RESEARCH 
ON  THE  SALT_^REQUIREMENTS 

OF 

REPRESENTATIVE  AGRICULTURAL  PLANTS 

PREPARED  FOR  A  SPECIAL  COMMITTEE 

OF   THE 

DIVISION  OF  BIOLOGY  AND  AGRICULTURE 

OF   THE 

NATIONAL  RESEARCH  COUNCIL 


EDITED    BY 

BURTON  E.  LIVINGSTON 


SECOND  EDITION 

Baltimore 


\2s 


Vv\ 


THE  FIRST  EDITION  OF  THIS  PLAN 
WAS  MIMEOGRAPHED,  AND  A  HUN- 
DRED COPIES  WERE  CIRCULATED.  THIS 
SECOND  EDITION  IS  ESSENTIALLY 
THE  SAME  IN  CONTENT  AS  THE  FIRST. 


HBAM  UBR*«V^GftICLa.TUWt: 


PREFACE 

During  the  war  period  the  Division  of  Agriculture,  Botany 
and  Zoology  of  the  National  Research  Council  established  a  spe- 
cial committee  to  attempt  the  organization  of  a  nation-wide  co- 
operation among  the  research  scientists  interested  in  plant  nutri- 
tion. The  project  is  of  fundamental  importance,  and  is  to  be 
continued  under  the  new  Council.  The  purpose  of  this  coopera- 
tion is  to  hasten  the  acquisition  of  definite  knowledge  regarding 
the  salt  requirements  of  a  few  representative  agricultural  plants, 
and  it  is  hoped  thus  to  accomplish  in  a  small  number  of  years 
what  would  usually  require  many  decades.  Experimenters  are 
earnestly  requested  to  further  this  work  in  every  way  possible, 
and  it  is  hoped  that  at  least  part  of  the  time  of  one  research 
worker  in  each  laboratory  where  this  kind  of  work  is  carried  on 
may  be  devoted  to  this  project.  If  all  of  the  time  of  one  or  more 
persons  can  be  devoted  to  the  work,  of  course,  that  would  be  still 
better  for  the  progress  of  knowledge  in  this  field. 

The  need  for  some  well-established,  correlated,  quantitative 
knowledge  of  the  salt  nutrition  of  plants  is  clearly  appreciated 
by  all  students  of  this  important  subject,  as  is  also  the  present 
almost  total  lack  of  such  knowledge.  Our  theories  are  incomplete 
and  vague,  and  the  experimentation  on  which  they  rest  has  not 
generally  been  such  as  to  allow  correlation  between  the  different 
pieces  of  work.  -  It  is  planned  that  the  present  cooperation  by  a 
large  number  of  experimenters  will  soon  furnish  a  great  body 
of  correlated  information  regarding  the  salt  requirements  of  the 
plants  studied ;  all  workers  in  the  project  are  urged  to  follow 
the  methods  described  on  the  pages  following  this  preface,  to 
the  end  that  all  results  obtained  may  be  as  truly  comparable  as 
possible.  While  each  cooperator  will  of  course  be  perfectly  free 
to  interpret  and  publish  his  results  as  he  may  see  fit,  the  com- 
mittee hopes  to  be  able  to  bring  all  the  contributions  together 
from  time  to  time  as  the  work  progresses,  so  as  to  build  up 
rapidly  a  rather  complete  statement  of  the  salt  requirements  of 
each  plant  that  is  included  in  the,  scheme. 

It  is  clear  that  this  project  is  a  physiological  one,  and  that  the 
results  obtained  cannot  be  expected  to  furnish  direct  and  imme- 
diate information  as  to  the  fertilizer  requirements  of  these  plants 
when  grown  on  any  agricultural  soil ;  each  soil  offers  its  own  set 

451805 


of  prob1errtS'-^.o  the  agronomist,  as  does  also  each  climate  and 
each  plant  form.  But  it  seems  safe  to  predict  that  the  correlated 
system  of  physiological  knowledge  that  is  to  result  from  this 
cooperation  will  place  in  the  hands  of  agronomists  and  agricul- 
tural chemists  many  valuable  facts  and  principles.  Upon  these, 
with  further  experimentation  in  the  field,  may  be  built  up  a 
greatly  improved  system  of  fertilizer  practice  and  crop  rotation. 
The  present  project  is  therefore  fundamental  to  the  rational 
advance  of  agricultural  science  and  practice. 

The  shortage  of  potassium  in  this  country  during  war  time 
emphasized  the  need  that  our  knowledge  of  the  best  ways  of 
using  fertilizer  salts  in  general  should  be  increased  and  put  on 
a  definite  basis  as  rapidly  as  possible.  This,  together  with  the 
high  price  of  nitrogen-bearing  fertilizer  material,  gave  to  this 
project  some  of  the  characteristics  of  a  war-emergency  problem, 
but  the  problem  is  exceedingly  important  and  fundamental  to 
agricultural  development  in  general.  A  concentrated  effort 
toward  the  building  up  of  a  reliable  body  of  American  scientific 
results  in  this  field  may  be  regarded  as  higjily  desirable  from  the 
standpoint  of  national  welfare.  Also,  the  fact  of  cooperation 
itself  should  benefit  American  science  very  greatly,  and  it  may 
be  hoped  that  this  general  method  of  advancing  knowledge  may 
eventually  become  much  more  common  among  democratic  peoples 
than  has  been  the  case  in  the  past.  Aside  from  war-emergency 
matters,  this  is  one  of  the  aims  set  forth  by  the  President  of  the 
United  States  in  his  executive  order  establishing  the  National 
Research  Council  on  a  permanent  basis. 

This  project  itself  contemplates  only  physiological  studies,  car- 
ried on  with  water  and  sand  cultures,  thus  avoiding  many  of 
the  complications  introduced  when  agricultural  soils  are  in- 
volved. Besides  determining  as  precisely  as  possible  what  are 
the  most  favorable  total  concentrations  and  sets  of  salt  propor- 
tions for  the  various  developmental  phases  of  the  plants  studied, 
it,  is  planned  to  include  experimental  studies  of  the  relative  de- 
grees of^susceptibility  to  fungus  attack  Exhibited  by  the  cultures 
in  different  solutions.  It  is  also  planned  to  obtain  chemical 
analyses  of  the  plants  grown  and  to  correlate  these  results  with 
the  characteristics  of  the  nutrient  media  used. 

The  problem  for  any  single  plant  is  so  complicated  in  itself, 
and  the  amount  of  logically  planned  and  carefully  carried-out 
experimentation  required  (before  even  tentative  conclusions  may 
be  attained)  is  so  great,  that  it  seemed  absolutely  necessary  at 
the  start  and  for  the  present  to  restrict  attention  to  a  very  few 


forms  of  plants.  The  work  has  been  begun  with  the  "Marquis" 
variety  of  spring  wheat,  and  an  attempt  will  be  made  to  advance 
our  knowldege  of  the  salt  requirements  of  this  plant  as  rapidly 
as  possible.  As  a  second  plant,  soy  bean  is  to  be  employed,  and 
work  upon  it  may  be  begun  immediately  if  workers  prefer  to 
deal  with  this  plant  rather  than  with  wheat.  In  the  beginning 
the  cooperation  is  to  be  limited  to  these  two  plants.  Other  plants 
may  be  taken  up  when  plans  and  methods  have  been  perfected 
and  when  the  work  may  be  well  enough  in  hand  so  that  the  co- 
operators  may  afford  to  leave  the  two  plants  just  mentioned. 
All  of  the  wheat  and  soy  bean  seed  used  will  be  supplied  by  this 
committee,  so  that  all  experimenters  may  be  considered  as  deal- 
ing with  the  same  complexes  of  internal  conditions  as  these  are 
presented  in  the  resting  seed.  Arrangements  have  been  made 
by  which  the  salts  employed  by  all  cooperators  may  also  be  of 
the  same  lots.  The  standardized  methods  to  be  employed  in  the 
beginning,  as  outlined  below,  are  based  on  those  of  Schreiner 
and  Skinner,  Tottingham,  Shive,  McCall,  and  Hibbard.  For  some 
references  to  the  literature  in  this  connection,  see  the  list  of 
citations  following  this  preface. 

Cooperators  are  asked  to  furnish  the  special  committee  with 
data,  as  the  work  progresses,  and  generally  to  keep  the  committee 
in  touch  with  their  work.  It  is  of  course  understood  that  the 
committee  will  give  proper  publicity  to  the  work,  with  due  credit 
to  all  cooperators. 

It  is  estimated  that  the  materials  and  apparatus  required  by 
one  worker  for  a  year  will  not  cost  more  than  $300.00,  supposing 
that  some  greenhouse  space  is  available  for  winter  work.  Much 
of  the  needed  apparatus  is  generally  at  hand  in  laboratories 
where  studies  in  plant  physiology  are  carried  on. 

Those  who  receive  copies  of  this  Plan  are  urged  to  look  over 
the  outline  of  the  project,  and  let  the  chairman  of  the  committee 
have  their  decisions  at  an  early  date,  as  to  what  they  may  be  able 
to  do  in  this  cooperation.*  It  is  desirable  to  have  as  large  a 
representation  as  possible  and  it  is  hoped  that  many  workers  may 
feel  that  this  is  their  project,  and  that  they  will  do  all  they  can 
to  further  it.  The  work  falls  readily  into  numerous  sections  of 
different  magnitudes,  so  that  a  cooperator  may  devote  only  a 
small  portion  of  his  time  to  it  and  still  obtain  valuable  results 
toward  the  general  solution  of  the  problem.     For  example,  if  a 


*  Correspondence  should  be  addressed  to  Dr.  B.  E.  Livingston,  Labora- 
tory of  Plant  Physiology,  The  Johns  Hopkins  Unli><^^^rsi!ty,(^aMij®3C<leLjVId. 

lI^boratory  por  soil  investigations, 

^UNIVERSITY  OF  MARYLAND, 
COLLEGE  PARK,  MD. 


worker  might  devote  only  an  hour  or  two  each  day  to  these 
experiments,  the  committee  would  be  able  to  aid  him  in  selecting 
a  small  number  of  solutions  for  comparison.  Every  little  piece 
of  careful  experimentation  (provided  only  that  it  fits  in  as  a  part 
of  the  general  plan)  will  count  in  the  general  summation. 

K.  F.  Kellerman, 

Wm.  Crocker, 

B.  E.  Livingston   (Chairman), 

Special  Committee  on  Salt  Requirements 
of  Representative  Agricultural  Plants, 
National  Research  Council,  Division  of 
Biology  and  Agriculture. 
DR.  A.  G.  McCALL, 
ARORATORY  POR  SOIL  INVESTIGATIONS, 
''NIVERSITY  OF  MARYLAND, 
■    ^    '  ^''■'^   IMRK,    MD. 


REFERENCES  TO  SOME  PAPERS  DESCRIBING  METHODS 

ON  WHICH  THE  PLAN  FOR  THIS 

PROJECT  IS  BASED.* 

1910.      Schreiner,  O.,  and  J.  J.  Skinner. 

Ratio  of  phosphate,  nitrate  and  potassium  on  absorption  and 
groAvth.  Bot.  Gaz.  50:  1-30.  1910.  Idem.  Some  effects  of  a 
harmful  organic  soil  constituent.  U.  S.  Dept.  Agric.  Bur.  Soils 
Bull.  70.     1910. 

1914.  Tottingham,  W.  E. 

A  quantitative  chemical  and  physiological  study  of  nutrient 
solutions  for  plant  cultures.    Physiol.  Res.  1 :  133-245.     1914. 

1915.  Shive,  J.  W. 

A  study  of  physiological  balance  in  nutrient  media.  Physiol. 
Res.  1 :  327-397.     1915. 

1916.  McCall,  A.  G. 

The  physiological  balance  of  nutrient  solutions  for  plants  in 
sand  cultures.  Soil  Sci.  2:  207-253.  1916.  Idem.  The  physio- 
logical requirements  of  wheat  and  soy  beans  growing  in  sand 
media.     Proc.  Soc.  Prom.  Agric.  Sci.  1916:  46-59.     1916. 

1917.  Hibbard,  R.  P. 

Physiological  balance  in  the  soil  solution.  Michigan  Agric. 
Exp.  Sta.  Techn.  Bull.  40.     1917. 

Shive,  J.  W. 

A  study  of  physiological  balance  for  buckwheat  grown  in 
three-salt  solutions.  New  Jersey  Agric.  Exp.  Sta.  Bull.  319. 
1917. 

1918.  Livingston,  B.  E.,  and  W.  E.  Tottingham. 

A  new  three-salt  nutrient  solution  for  plant  cultures.  Amer. 
Jour.  Bot.  5:  337-346.     1918. 


*'0f  course  a  large  number  of  papers  might  be  mentioned  in  this  list,  as 
bearing  in  one  way  or  another  upon  this  project.  From  the  point  of  view 
of  the  logical  analysis  of  the  problem  the  papers  cited  heFe  will  be  specially 
valuable,  and  "numerous  other  literature  references  may  be  obtained  from 
them.  Tottingham's  bibliography  will  be  found  very  useful  in  connection 
with  the  general  proposition  of  controlled  chemical  environment  as  far  as 
the  root  system  of  the  plant  is  concerned. 


McCall,  A.  G.,  and  P.  E.  Richards. 

Mineral  food  requirements  of  the  wheat  plant  at  different 
stages  of  its  development.  Jour.  Amer.  Soc.  Agron,  10:  127-134. 
1918. 

Shive,  J.  W.,  and  W.  H.  Martin. 

A  comparison  of  salt  requirements  for  young  and  for  mature 
buckwheat  plants  in  water  cultures  and  sand  cultures.  Amer. 
Jour.  Bot.  5:  186-191.  1918.  Idem.  A  comparative  study  of 
salt  requirements  for  young  and  for  mature  buckwheat  plants  in 
solution  cultures.    Jour.  Agric.  Res.  14:  115-175.     1918. 

Schreiner,  O.,  and  J.  J.  Skinner. 

The  triangle  system  for  fertilizer  experiments.  Jour.  Amer. 
Soc.  Agron.  lO:  225-246.     1918. 


INTRODUCTION. 

This  project  aims  to  test  a  large  number  of  combinations  of  the 
necessary  chemical  elements,  to  find  out  what  combinations  give 
the  most  satisfactory  growth  of  the  plants  considered.  Different 
phases  of  the  development  of  the  plants  are  to  be  treated  sepa- 
rately, to  bring  out  any  changes  in  the  •nutritional  requirements 
that  may  supervene  as  gi*owth  proceeds.  As  many  different  com- 
plexes of  climatic  conditions  as  are  practicable  are  to  be  tested, 
to  find  out  in  how  far  the  salt  requirements  may  depend  upon 
climatic  conditions.  It  is  planned  to  find  out  just  what  sets  of  ^ 
salt  conditions  give  the  best  growth  for  each  type  of  climatic 
complex. 

The  project  thus  contemplates  a  very  thorough  experimental 
study  of  the  physiological  possibilities  of  the  plants  dealt  with. 
Just  as  the  atomic  weights  of  the  chemical  elements  need  to  be 
known  with  considerable  precision  before  their  relations  to  their 
surroundings  may  be  satisfactorily  studied,  so  the  physiological 
characteristics  of  agricultural  plants  need  to  be  known  before 
scientific  agriculture  may  progress  very  far. 

The  cooperative  feature  of  the  project  aims  to  secure  a  large 
body  of  comparable  data  as  rapidly  as  possible.  A  large  number 
of  research  workers  acting  simultaneously  will  be  able  to  test 
the  numerous  possibilities  in  a  comparatively  short  time,  and  the 
fact  that  all  employ  the  same  standard  methods  should  make  all 
of  the  results  fit  into  one  general  whole. 

The  following  outline,  which  is  planned  to  be  extended  and 
improved  later,  has  been  elaborated  through  consultation  with 
a  large  number  of  specialists  in  this  sort  of  work.  It  is  hoped 
that  the  essentials  of  the  method  here  described  will  be  followed, 
since  likeness  of  method  is  the  prime  consideration  in  work  of 
this  sort.  When  alterations  of  the  plan  seem  necessary  the  other 
cooperators  should  be  informed  and  an  agreement  reached 
through  the  committee.  Correspondence  regarding  the  work 
should  be  addressed  to  Dr.  B.  E.  Livingston,  Laboratory  of  Plant 
Physiology,  the  Johns  Hopkins  University,  Baltimore,  Md. 

DR.  A.  G.'McCALL, 

THE  PLAisA^WJOgi^  H^SeM"-  investigations, 

UNIVERSITY  OF  MARYLAND 
The  first  and  most  important  plant  for  the  present  purpo'se  is 

wheat,  and  a  supply  of  seed  of  the  ":fe^'rli&'S^  ^?fkj^%  spring 

wheat  was  obtained  by  purchase  from  Professor  Leith,  of  the 

Wisconsin  Agricultural  Experiment  Station.     Cooperators  will 


receive  seed  from  Baltimore,  upon  request.     A  new  supply  will 
be  available  in  the  fall  of  1919. 

The  second  plant  to  be  studied  is  soy  bean,  and  a  supply  of  seed 
has  been  made  available  through  the  kindness  of  Mr.  J.  E. 
Metzger  of  the  Maryland  Agricultural  Experiment  Station.  This 
seed  may  also  be  obtained  from  Baltimore,  on  request. 

TWO  METHODS  OF  CULTURE. 

It  is  planned  to  carry  out  this  elaborate  series  of  physiological 
tests  with  both  water  and  sand  cultures,  but  it  seems  desirable  to 
press  forward  somewhat  more  rapidly  with  the  former;  most 
workers  may  prefer  to  attack  the  water  cultures  first,  since  the 
operations  are  simpler  here.  Both  methods  are  set  forth  below. 
Special  details  for  soy  bean  and  for  the  later  phases  of  wheat 
are  still  to  be  elaborated  and  modifications  of  the  outline  here 
given  may  be  required  as  the  work  progresses. 

WATER  CULTURE  OF  WHEAT. 
Four  Developmental  Phases. 

The  development  of  the  plant  will  be  considered  in  four  sepa- 
rate stages  or  phases,  three  of  these  being  defined  by  the  degree 
of  development  attained  and  the  other  by  time  duration.  These 
phases  are  as  follows: 

1.  Germination  Phase,  from  beginning  of  soaking  till  the 
shoot  is  four  centimeters  high,  measured  from  the  seed  to  the  tip 
of  the  shoot. 

2.  Seedling  Phase,  from  the  end  of  phase  1  for  a  period  of 
five  iveeks,  without  regard  to  the  size  of  the  plant. 

3.  Vegetative  Phase,  from  the  end  of  phase  2  until  the  first 
appearance  of  flowering  in  the  controls.  [Controls  are  always  in 
Shive's  best  solution  for  wheat  seedlings,  IR5C2,  by  1/10-incre- 
ments  (1.75  atm.)  ;  see  below.] 

Jf.  Reproductive  Phase,  from  the  end  of  phase  3  until  ma- 
turity is  reached  by  the  best  five  cultures  of  the  group  of  20  or  21. 

These  phases  ghould  be  adhered  to  with  care,  in  order  that  all 
the  parts  of  the  work  may  be  comparable.  It  may  be  that  their 
definition  will  require  alteration  after  the  work  is  well  in  hand, 
but  the  definitions  here  given  will  serve  for  the  beginning. 

It  is  aimed  first  to  find  out  what  four  solutions  should  be 
consecutively  used  to  produce  plants  that  are  the  best  at  the  ends 
of  all  four  stages  of  development.  Thus,  after  the  plan  has  been 
carried  out  we  should  be  able  to  say  that  phase  1  should  have 

10 


solution  a;  phase  2,  solution  b;  phase  3,  solution  c;  and  phase  4, 
solution  d.  Many  other  possibilities  are  clearly  in  the  prospect, 
but  this  plan  appears  to  be  best  for  the  first  study.  It  is  not  at 
all  well  known  how  the  solution  requirements  for  best  growth 
may  alter  from  one  developmental  phase  to  the  next  succeeding 
one,  nor  is  it  known  what  may  be  the  most  satisfactory  method 
of  dividing  the  growth  period  into  partial  periods  to  represent 
the  phases.  The  scheme  of  employing  these  four  phases  and 
attempting  to  find  the  best  solutions  for  each  phase  (the  preced- 
ing phase  or  phases  having  had  their  own  best  solutions)  is 
simple  and  readily  practicable  for  making  a  start.. 

1.     Germination  Phase. 

General  Treatment  of  Seed.  The  supply  of  seed  should  be 
stored  in  a,  loosely  closed  container,  with  some  access  of  air,  and 
in  a  dry,  cool  place,  free  from  laboratory  gases,  etc.  The  seed 
to  be  used  in  any  test  should  be  inspected,  and  obviously  imper- 
fect or  otherwise  apparently  undesirable  seeds  should  be  dis- 
carded. Soak  ten  times  as  many  seeds  as  the  number  of  seedlings 
needed,  for  five  or  six  hours  in  a  glass  vessel,  with  a  volume  of 
germination  solution  equal  to  twice  their  apparent  volume.  Then 
place  them  on  the  germination  net. 

The  seeds  should  be  uniformly  distributed  over  the  germina- 
tion net.  Since  excretion  and  absorption  by  the  seeds  on  the 
germinating  net  tend  to  alter  the  germinating  solution,  care 
should  be  taken  that  the  seeds  are  not  too  crowded  on  the  net. 
Germination  is  to  be  continued  until  the  shoots  reach  a  height  of 
four  centimeters,  measured  from  the  seed.  A  uniform  series  of 
seedlings  is  then  to  be  selected  and  placed  in  the  culture  jars.  The 
treatments  for  the  four  phases  for  wheat  will  now  be  presented. 
Later  modifications  may  be  required,  especially  for  the  last  two 
phases. 

Germination  Apparatus  and  Method.  For  germinating  the 
seeds  the  following  scheme  is  to  be  followed,  at  least  in  its  essen- 
tials. This  is  not  necessarily  the  best  plan  conceivable,  but  it  is 
one  fairly  good  way,  and  it  is  thought  to  be  well  adapted  to  the 
various  exigencies  of  a  large  number  of  laboratories  and  work- 
ers. Uniformity  of  method  among  the  various  cooperators  is 
again  to  be  emphasized  here  as  absolutely  requsite.  Failure  to 
adhere  to  the  standard  method  would  effectually  prevent  the 
different  sets  of  results  from  being  comparable.  If  modifications 
are  planned,  the  committee  should  be  informed  in  this  regard. 

11 


The  germination  net  consists  of  ordinary  mosquito  netting, 
thoroughly  paraffined  by  dipping  in  melted  "Parawax"  (or  other 
paraffin  of  equally  high  melting  point) .  The  net  is  to  be  tied 
as  tightly  as  possible  over  the  top  of  the  germination  jar.  A 
new  net  should  be  used  for  each  germination. 

The  germination  jar  is  an  ordinary  5-gallon  stoneware  jar, 
approximately  28  cm,  in  inside  diameter  and  34  cm.  high,  glazed 
inside  and  out.  The  germination  net  should  be  tied  tightly  over 
the  opening  of  the  jar,  so  that  when  the  jar  is  filled  with  solution 
the  water  surface  practically  coincides  with  the  plane  of  the  net. 

Insert  in  the  jar  a  vertical  glass  tube,  which  will  lie  close  to 
the  jar  wall  and  project  a  few  centimeters  above  the  net,  through 
which  it  passes.  This  tube  should  be  broken  obliquely  at  its 
lower  end,  where  it  rests  on  bottom  of  jar.  The  upper  end  should 
be  cut  squarely  off.  The  bore  of  the  tube  should  be  about  a  cen- 
timeter, or  more.  New  solution  is  added  through  this  tube,  so 
as  to  be  introduced  at  bottom  of  jar. 

From  a  suitable  support  above,  a  glass  thermometer  is  to  be 
suspended  vertically,  so  that  its  bulb  lies  just  entirely  below  the 
net,  extending  through  the  latter  at  its  center.  This  shows  the 
temperature  of  the  solution  that  lies  about  the  seeds. 

It  is  aimed  to  maintain  the  temperature  for  germination 
within  about  2°  C,  and  it  will  therefore  be  necessary  generally 
to  place  the  whole  jar  in  a  larger  water-bath,  to  which  cold  or 
warm  water  may  be  added  two  or  three  times  a  day,  according 
to  the  needs  of  the  temperature  control.  A  better  form  of  con- 
trol may  of  course  be  used ;  this  method  "by  hand"  is  taken  as 
the  simplest  and  least  expensive.  An  ordinary  galvanized  iron, 
wooden  or  fiber  wash-tub  is  suitable  for  the  bath  in  which  the 
germination  jar  stands.  The  bath  water  should  not  reach  as 
high  as  the  edge  of  the  netting  where  the  latter  projects  over 
the  edge  of  the  jar. 

The  apparatus  should  stand  in  a  lighted  place,  subject  to  the 
ordinary  fluctuation  of  day  and  night,  free  from  poison  gases  and 
laboratory  fumes,  but  should  not  receive-  direct  sunshine  at  any 
time.  It  should  be  so  placed  that  the  overflow  will  be  drained 
away.  Ordinary  water  is  used  for  the  bath;  nutrient  solution 
for  the  jar.  Solution  is  added  to  the  jar  once  a  day  during 
germination,  and  water  is  added  to  the  bath  as  frequently  as  may 
be  necessary  to  obtain  the  needed  temperature  control.  In  both 
cases  there  will  of  course  be  an  overflow,  the  water  solution  from 
the  jar  rising  through  the  net  and  passing  over  into  the  tub. 


12 


The  jar  is  filled  at  the  start  with  the  solution  to  be  used  and 
two  liters  of  new  solution  is  added  once  each  day,  by  means  of 
a  siphon  or  funnel,  the  new  solution  entering  through  the  glass 
tube  above  mentioned.  The  same  kind  of  solution  is  to  be  used 
throughout  the  germination  period. 

Tests  on  the  relation  of  the  nature  of  the  solution  and  its  tem- 
perature to  rapidity  of  germination  in  the  wheat  to  be  employed 
have  been  carried  out  at  Baltimore,  and  one  of  the  best  tempera- 
tures and  sets  of  salt  proportions  for  this  wheat  has  proved  to  be 
25°  C.  and  Shive's  solution  R5C2  (0.175  atm.).  The  germina- 
tion temperature  is  to  be  maintained  at  from  24°  to  26°  C,  and 
the  solution  to  be  used  is  Shive's  R5C2;  in  1/10  "optimal"  total 
concentration  (osmotic  value  about  0.175  atm.).  This  solution 
has  the  following  volume-molecular  partial  concentrations  of 
the  three  salts;  KH^POs  0.0018  mol.;  Ca(NOOs  0.00052  mol. ; 
MgSOs  0.0015  mol.  No  ferric  phosphate  is  to  be  used  in  the  solu- 
tion for  the  germination  phase  of  growth.  This  solution  may 
safely  be  prepared,  for  stock,  thirty  times  as  concentrated  as  is 
required,  so  that  67  cc.  of  the  stock  solution  plus  two  liters  of 
water  will  give  a  rather  close  approximation  to  the  needed  germi- 
nation solution. 

This  stock  solution  from  which  the  germination  solution  is  to 
be  prepared  by  dilution  (and  from  which  the  control  solution 
for  later  phases  of  growth  is  also  to  be  prepared,  with  the  addi- 
tion of  FePO<  in  that  case)  thus  has  the  following  volume- 
molecular  partial  concentrations  of  the  three  salts  (these  values 
being  thirty  times  the  corresponding  values  given  above)  ; — 
K&POs  0.054  mol.;  Ca(NOOs  0.0156  mol.;  MgSOs  0.045  mol. 
To  prepare  the  two  liters  of  germination  solution  required  daily, 
add  67  cc.  of  this  stock  solution  to  two  liters  of  water.  The 
"error"  is  negligible  and  this  quick  method  conserves  time. 

The  seedlings  to  be,  placed  in  the  culture  jars  for  the  seedling 
phase  are  to  be  selected  for  uniformity  as  to  height  (4  cm.)  and 
general  appearance.  Since  ten  times  as  many  seeds  are  to  be 
placed  on  the  net  as  are  to  be  needed  after  germination,  this 
selection  should  be  as  satisfactory  as  is  possible  with  present 
knowledge. 

It  is  convenient  to  select  at  once  all  the  seedlings  to  be  used 
(and  some  extra  ones),  lifting  them  from  the  germination  net 
with  care  not  to  injure  the  roots  nor  to  bring  them  into  even 
momentary  contact  with  the  hands,  table,  etc.  The  seedlings 
thus  selected  are  placed  in  one  or  more  glass  pans  with  germina- 
tion solution  2  cm.  deep,  so  that  the  roots  are  in  the  solution  and 

13 


the  shoots  project  above  its  surface.  Then  they  are  taken  from 
these  pans,  one  by  one,  and  fixed  in  the  prepared  cork  stoppers. 
They  should  not  be  placed  in  distilled  water  or  tap  water  at  all, 
but  are  thus  kept  in  the  germination  solution  until  they  are 
actually  placed  in  the  culture  jars.  Have  the  hands  clean ; 
paraffined  forceps  are  useful. 

2.     Seedling  Phase. 

Culture  Jars  and  Corks,  and  the  Setting  Up  of  Cultures.  The 
culture  jars  used  for  the  seedling  phase  are  to  be  ordinarily  glass 
fruit  jars,  of  the  "Mason"  type,  the  quart  size.  It  is  essential 
only  that  the  capacity  be  approximately  correct  and  that  the 
opening  be  suitable  for  the  corks  carrying  the  seedlings.  One 
distinct  advantage  of  the  "Mason"  jar  is  that  it  is  supplied  in 
three  sizes  (pint,  quart  and  two-quart) ,  all  with  the  same  size  of 
opening;  another  advantage  is  that  this  jar  is  procurable  prac- 
tically everywhere  in  the  United  States,  and  at  a  low  price. 
The  tops  supplied  with  the  jars  are  not  needed  in  this  work. 

Each  jar  is  to  be  covered  by  a  cylindrical  jacket  of  opaque 
paper,  white  on  the  outside,  to  keep  strong  light  from  reaching 
the  roots  of  the  plants.  It  is  desirable  that  the  jacket  be  so 
arranged  that  it  can  be  readily  removed  without  disturbing  the 
plants  (for  examination  of  the  root  systems,  etc.).  A  good 
method  is  that  employed  by  Shive  (1915) .  A  jacket  that  is  dark- 
colored  on  the  outside  is  not  suitable,  since  absorption  of  radiant 
energy  is  undesirable. 

The  corks  used  for  closing  the  jars  and  for  supporting  the 
seedlings  should  be  of  good  quality,  of  the  flat  form,  one-half 
inch  thick  and  of  a  diameter  to  fit  the  opening  of  the  jar  used. 
They  are  to  be  thoroughly  impregnated  and  thinly  coated  with 
paraflfin,  such  as  "Parawax."  A  very  excellent  arrangement  for 
mounting  the  seedlings  is  that  adopted  by  Tottingham  (1914). 
Only  five  seedlings  per  jar  will  be  used  in  the  present  coopera- 
tion. It  is  strongly  urged  that  this  arrangement  be  employed, 
for  the  sake  of  uniformity,  but  if  another  arrangement  is  used  it 
should  conform  in  the  essentials.  Those  essentials  are :  that  the 
five  seedlings  must  be  firmly  held  just  above  the  seed  in  each 
case,  with  but  slight  pressure  opposed  to  subsequent  increase  in 
the  stem  diameter  in  this  region;  that  the  jar  be  practically 
closed;  that  the  stopper  be  protected  from  fungi;  and  that  the 
technique  of  placing  the  seedlings  be  simple  (so  as  to  be  rapid 
and  to  avoid  undue  disturbance  of  the  delicate  plantlets  during 
the  process  of  placing) .    Ready-prepared  corks  may  be  obtained 

14 


from  the  committee  at  cost, — perforated  ones  $4.00  per  hundred, 
plain  ones  $3.50  per  hundred.  Corks  require  reparaffining  from 
time  to  time  if  they  show  fungus  growth.  The  same  corks  are  to 
be  used  for  later  growth  phases. 

A  good  quality  of  ordinary  cotton  (batting)  is  best  for  fixing 
the  seedlings  in  the  corks;  absorbent  cotton  is  not  desirable  (it 
absorbs  water  much  more  readily  than  ordinary  cotton) .  Use 
just  enough  cotton  to  hold  the  seedling  securely  in  position,  so 
that  it  will  not  slip  downward.  The  cotton  will  become  com- 
pressed, as  the  stem  enlarges.    The  cotton  is  to  be  kept  dry. 

Jars  should  be  thoroughly  washed,  rinsed  in  distilled  water, 
and  dried  (or  each  finally  rinsed  with  the  solution  to  be  used 
therein)  before  using.  Each  is  filled  to  a  point  1  cm.  below  the 
lower  surface  of  the  cork.  A  non-perforated,  paraffined  cork  is 
inserted  (to  reduce  evaporation  and  other  changes  during  the 
interim)  and  the  jar  is  clearly  marked  with  its  solution  number 
(wax  pencil).  When  all  the  jars  of  a  series  are  thus  filled  and 
marked,  the  work  of  placing  the  seedlings  is  taken  up,  the  cork 
bearing  the  five  seedlings  now  replacing  the  non-perforated  cork 
that  previously  stoppered  the  jar.  After  each  jar  is  supplied 
with  seedlings  its  jacket  is  put  in  place.  The  jacket  should  also 
bear  the  number  of  the  solution  contained  in  its  jar  (marked  in 
pencil) . 

The  seedlings  should  be  kept  from  direct  sunlight  and  from 
laboratory  gases  or  other  disturbing  influences  throughout  the 
process  of  changing  from  germination  apparatus  to  jars,  and  the 
series  of  jars  is  to  be  placed  in  the  experiment  location  as  soon 
as  all  are  ready.  It  is  desirable  that  the  placing  of  all  the  seed- 
lings for  any  comparable  series  be  completed  as  rapidly  as  pos- 
sible, on  the  same  day;  the  jars  may  be  supplied  with  their  solu- 
tions on  the  preceding  day,  but  are  then  to  be  kept  stoppered, 
as  described  above. 

Any  series  may  be  set  up  either  as  a  simple  series  or  in  dupli- 
cate, triplicate,  etc.,  according  to  the  number  of  cultures  in- 
cluded, the  time  at  the  disposal  of  the  experimenter,  etc.  In  all 
cases  the  control  culture  should  be  in  triplicate;  i.  e.,  three  cul- 
tures in  solution  IR5C2  (1/10-increments,  1.75  atm.)  are  to  be 
included  in  every  series. 

Renewal  of  Solutions,  and  Observations  During  the  Five-Week 
Period  of  the  Seedling  Phase.  The  solution  of  each  culture  is  to 
be  renewed  every  31/2  days  (nine  renewals  in  the  five- week 
period).     Details  regarding  the  renewals  are  given  below,  also 


16 


regarding  the  preparation  of  the  solutions,  the  experiment  loca- 
tion and  exposure,  and  the  records  of  aerial  conditions. 

Records  are  to  be  kept  of  visual  observations  made  at  the  times 
the  solutions  are  renewed,  regarding  differences  that  may  be 
manifest  among  the  various  cultures.  Attention  should  be  given 
to  the  root  systems  as  well  as  to  the  tops  of  the  plants.  It  is  pos- 
sible that  a  culture  showing  the  apparently  most  vigorous  plants 
of  a  series  at  the  end  of  the  third  week,  for  example,  may  not 
show  the  most  vigorous  plants  at  the  end  of  the  fifth  week,  etc., 
and  these  records  of  visual  observation  are  planned  to  bring  out 
such  occurrences.  Without  such  records  important  features  may 
escape  notice  entirely.  (On  comparing  cultures,  etc.,  when  meas- 
urements cannot  be  employed,  see: — Free,  E.  E.  Plant  World 
18:249-256.     1915. 

Plant  Measurements  at  End  of  Five-Week  Period.  At  the  end 
of  the  seedling  phase  the  following  plant  measurements  are  to  be 
made : — 

(1)  Length  of  longest  and  shortest  top  in  each  culture,  meas- 
ured from  the  seed  (or  the  position  where  it  was  attached)  to  the 
extreme  tip  of  the  plant. 

(2)  Fresh  weight  of  tops  for  each  culture  as  a  whole.  Cut  off 
each  main  root  at  its  junction  with  the  stem  and  consider  all 
that  remains  as  the  top  of  the  plant.  Cut  tops  into  pieces  as 
much  as  is  necessary,  and  immediately  place  all  tops  from  each 
single  culture  in  a  weighed  test-tube,  stoppering  with  rubber  or 
paraffined  cork  stopper.  Stopper  is  removed  when  weighing 
occurs.  Weigh  as  soon  as  possible,  and  record  fresh  weight  of 
tops  for  each  culture  as  a  whole.  Calculate  this  value  to  repre- 
sent 5  plants  in  every  case  where  the  entire  5  plants  are  not 
available. 

(3)  Dry  weight  of  tops  for  each  culture  as  a  whole.  After 
fresh  weight  has  been  obtained,  dry  the  tops,  at  a  lower  tempera- 
ture first  and  then  at  102°  C,  and  determine  dry  weight.  It  is 
well  to  place  tubes  in  a  desiccator  on  removal  from  drying  oven 
and  to  stopper  each  tube  as  it  is  weighed,  using  the  same 
weighed  rubber  or  paraffined  cork  stopper  for  all  tubes;  this 
avoids  having  a  large  number  of  weighed  stoppers.  Of  course 
other  weighing  vessels,  etc.,  may  be  used ;  the  method  above  sug- 
gested seems  adequate  and  is  simple  and  inexpensive. 

(4)  Dry  weight  of  roots  for  each  culture  as  a  whole.  Place 
all  root  systems  from  single  culture  together  and  press  gently 
between  sheets  of  blotting  paper  to  remove  most  of  the  liquid. 


16 


Then  dry  in  weighed  test-tube,  as  for  tops,  and  obtain  the  dry 
weight  of  roots.    Other  suitable  methods  may  of  course  be  used. 

(5)  Dry  weight  of  entire  plants  for  each  culture  as  a  whole. 
This  datum  is  simply  the  sum  of  the  corresponding  dry  weights 
of  tops  and  roots. 

(6)  Record  any  differences  that  may  be  manifest,  but  not 
measurable  in  the  above  terms.  Of  course  these  observations 
are  to  be  made  before  plants  are  removed  from  the  jar  and  stop- 
per, and  the  whole  manipulation  of  getting  the  above  measure- 
ments is  to  be  carried  out  so  as  to  prevent  appreciable  changes  in 
fresh  weight  before  this  is  measured.  Treat  each  culture  sepa- 
rately till  its  tops  are  in  the  stoppered  tube,  then  proceed  to  next 
culture.  Preserve  the  dry  material  in  envelopes,  properly 
marked,  so  that  a  reweighing  or  other  future  examination  may 
be  made  if  desirable. 

3.     Vegetative  Phase. 

Preparation  of  the  Plants.  Germination  is  to  be  carried  out 
as  for  the  seedling  phase,  and  twice  as  many  jars  are  to  be  set 
up  for  the  seedling  phase  as  will  be  needed  for  the  vegetative 
phase.  These  cultures  are  to  be  carried  through  the  seedling 
phase  in  the  manner  described  for  that  phase,  but  all  cul- 
tures  ARE   TO    BE    SUPPLIED    WITH    THE    SAME    SOLUTION,    which 

is  the  one  previously  found  to  be  best  for  the  seedling  phase. 
At  the  end  of  the  five-week  period  there  should  be  twice  as 
many  plants,  all  nearly  alike,  as  are  to  be  needed  for  the 
vegetative  phase.  Select  five  or  ten  plants  from  this  lot  to 
represent  the  average,  and  record  for  them  the  final  measure- 
ments of  the  seedling  phase,  as  stated  above.  From  the  remain- 
ing plants  select  a  uniform  lot  for  the  vegetative  phase.  It  will 
generally  not  be  necessary  to  remove  plants  from  their  corks; 
the  cork  and  its  plants  will  simply  continue  in  one  of  the  cultures 
of  the  vegetative  phase.  All  cultures  are  of  course  left  in  the 
solution  used  for  the  seedling  phase  until  transferred  to  the  par- 
ticular solution  to  be  used  for  that  culture  in  the  vegetative 
phase.  Plants  that  are  not  needed  are  to  be  discarded  after  the 
series  for  the  vegetative  phase  is  entirely  set  up.  Of  course, 
duplicate,  triplicate,  etc.,  cultures  may  be  employed;  and  tripli- 
cate control  is  to  be  included,  as  in  the  seedling  phase. 

Treatment  During  the  Vegetative  Phase.  All  the  different 
solutions  (see  below)  are  to  be  tested  for  the  vegetative  phase, 
to  find  out  what  solution  is  best  for  this  phase,  as  will  have  been 
done  for  the  seedling  phase.    The  procedure  is  the  same  as  for 

17 


the  seedling  phase,  with  solutions  renewed  twice  per  week.  It 
may  be  necessary  to  furnish  the  plants  with  mechanical  support. 
The  basis  of  the  support  should  be  a  cylindrical  wooden  stake 
(1/4 -inch  dowel  is  good)  and  care  should  be  exercised  that  the 
leaves  are  not  seriously  crowded.  The  support  described  by 
Hibbard  (1917)  is  one  satisfactory  form.  The  stake  is  set  in  the 
center  of  the  cork  in  which  the  plants  are  arranged.  This  phase 
ends  when  flowers  appear  in  the  controls,  but  this  statement  may 
require  modification  as  the  work  progresses. 

Plant  Measurements  at  End  of  Vegetative  Period.  These  are  to., 
be  the  same  as  those  made  at  end  of  seedling  period.  Of  course 
visual  observations  on  the  plants  are  to  be  made  from  time  to 
time  through  the  vegetative  period,  just  as  in  the  case  of  the 
seedling  period.  Especially  should  the  final  records  show  obser- 
vations on  differences  in  inflorescence,  for  those  cultures  that 
show  flowers. 

4.     Reproductive  Phase. 

Preparation  of  the  Plants.  Germination  is  to  be  carried  out 
as  for  earlier  phases  and  twice  as  many  jars  are  to  be  set  up  for 
the  seedling  phase  as  will  be  needed  for  the  reproductive  phase. 
These  cultures  are  all  to  be  carried  through  the  seedling  phase 
(with  the  best  solution  for  that  phase)  just  as  in  preparation 
for  the  vegetative  phase.  Then  a  selection  of  one  or  two  repre- 
sentative cultures  is  made,  for  records  of  plant  measurements 
of  the  seedling  phase,  and  the  remainder  are  carried  through  the 
ve.getative  phase,  but  all  with  the  ^ame  solution,  which 
has  been  found  to  be  best  for  that  phase.  At  the  end  of 
the  vegetative  phase  one  or  two  cultures  are  selected  to  repre- 
sent the  average,  records  are  made  of  plant  measurements  from 
these  for  the  vegetative  phase,  and  the  remainder  furnish  the 
selection  for  the  reproductive  phase.  This  selection  is  made  just 
as  in  the  case  of  the  vegetative  phase  described  above.  The 
series  may  of  course  be  in  duplicate,  etc. ;  and  triplicate  control 
is  introduced  as  in  earlier  phases. 

Treatment  During  the  Reproductive  Phase.  -All  of  the  solu- 
tions (see  below)  are  to  be  tested  for  the  reproductive  phase. 
The  procedure  is  the  same  as  for  the  two  preceding  phases,  with 
renewal  of  solutions  twice  per  week.  The  plants  will  probably 
need  mechanical  support.  This  phase  continues  till  maturity  is 
reached  by  the  best  plants  of  the  series.  The  exact  criteria  to  be 
used  may  receive  more  attention  as  the  work  proceeds;  it  is  of 
course  aimed  to  find  out  what  set  of  salt  proportions  is  best  for 

18 


the  reproductive  phase,  when  the  plants  have  previously  been 
supplied  with  the  respectively  best  solutions  for  the  germination, 
seedling  and  vegetative  phases. 

Plant  Measurements  at  End  of  Reproductive  Period.  These 
are  to  be  generally  the  same  as  those  made  at  the  ends  of  the 
preceding  periods,  but  it  will  be  desirable  to  separate  the  grain 
produced  from  the  rest  of  the  tops  in  the  present  case.  The  dry 
weight  of  grain  is  to  be  determined,  also  the  number  of  grains. 
Of  course  visual  observations  are  to  be  made  from  time  to  time 
during  the  reproductive  phase,  with  special  attention  given  to 
flowering  and  fruiting. 

Renewal  of  Solutions. 

The  solution  placed  in  any  culture  jar  as  the  beginning  of  an 
experiment  is  to  be  completely  discarded  and  replaced  by  a  fresh 
one  of  the  same  composition,  after  31/2  days,  and  this  renewal  of 
every  solution  is  to  occur  at  31/2 -day  intervals  (twice  per  week, 
thus  avoiding  Sunday  renewals)  throughout  the  course  of  the 
experiment.  The  following  points  apply  to  all  growth  phases 
alike. 

Before  the  renewals  are  to  be  made,  a  new  set  of  jars  are  pre- 
pared, as  at  the  beginning,  each  filled  with  its  proper  solution 
and  properly  marked  and  stoppered  with  non-perforated  cork. 
Then  these  jars  are  placed  near  the  series  of  cultures  and  each 
stopper,  bearing  its  plants,  is  removed  from  its  original  jar  and 
placed  in  the  new  jar  of  corresponding  number.  In  making  the 
change,  care  is  of  course  to  be  taken  not  to  injure  the  roots  nor 
to  disturb  them  more  than  is  unavoidable.  Finally,  the  opaque 
jackets  are  transferred  to  the  new  jars,  and  the  old  jars  are 
emptied,  the  volume  of  the  contents  is  recorded,  and  they  are 
washed,  to  be  used  again  at  the  next  renewal. 

The  purpose  of  determining  the  volume  of  solution  remaining 
in  each  jar  at  each  renewal  is  to  furnish  data  on  the  relative 
amounts  of  water  absorbed  by  the  various  cultures.  The  volume 
of  solution  originally  placed  in  each  jar  will  of  course  be  known, 
and  this  value  minus  the  volume  left  after  31/2  days  will  repre- 
sent the  volume  absorbed  in  that  period.  The  rate  of  absorption 
is  approximately  the  same  as  the  rate  of  transpiration  for  such 
plants  as  we  deal  with.  Of  course  this  volume  measurement 
need  not  be  of  great  precision ;  a  plus  or  minus  error  of  as  much 
as  3  or  4  per  cent,  is  probably  allowable  until  results  indicate 
necessity  for  greater  precision.  It  should  be  added  that  a  better 
method  of  dealing  with  this  feature  is  to  weigh  each  culture  be- 

»  19 


fore  and  after  each  filling  of  the  jar  with  fresh  solution.  It  is  de- 
sirable to  employ  the  weighing  method  for  such  work  as  this,  but 
experience  suggests  that  many  experimenters  prefer  the  volu- 
metric method.  Either  will  serve  our  purpose,  however.  In 
either  case  the  desideratum  is  to  have  a  record  of  the  approxi- 
mate amount  of  solution  removed  from  each  jar  during  each 
three  and  one-half  day  period. 

Experiment  Location  and  Exposure. 

The  cultures  are  to  be  exposed  generally  in  a  greenhouse,  but 
at  some  stations  they  may  be  out  of  doors.  In  any  event,  they 
are  to  receive  the  climatic  light  (with  shade,  as  of  painted  glass, 
etc.,  only  when  this  seems  necessary  in  order  that  the  plants  may 
thrive),  but  they  must  not  receive  any  rain.  For  the  colder 
months  at  most  stations  the  temperature  will  be  artificially 
much  above  the  climatic  temperature.  When  artificial  heat  is 
not  considered  as  necessary  it  will  of  course  be  omitted ;  in  gen- 
eral, any  greenhouse  in  which  other  plants  are  kept  growing 
should  be  suitable  for  these  cultures.  It  is  planned  to  carry  out 
these  tests  with  a  large  number  of  climatic  complexes,  such  as 
will  be  obtained  by  employing  a  large  number  of  geographical 
locations  and  various  seasons  of  the  year  at  each  station. 

The  special  problem  of  uniform  exposure  to  the  aerial  complex 
of  conditions  (uniform  for  all  cultures  of  any  comparable  series) 
is  of  considerable  importance,  and  it  is  hoped  that  all  experi- 
menters will  use  rotating  tables.  This  point  has  been  discussed 
by  Shive  (1915) ,  who  describes  one  way  to  build  a  rotating  table 
for  this  sort  of  work.  It  is  desirable  that  all  cultures  that  are  to 
be  comparable  should  stand  on  the  table  in  a  single  circle;  two 
circles  of  them  form  two  series  with  slightly  different  aerial 
surroundings,  although  the  different  cultures  of  any  one  circle 
are  themselves  comparable.  (If  a  rotating  table  cannot  be  em- 
ployed, the  cultures  should  be  shifted  on  the  bench  so  as  to  pass 
through  each  position  of  exposure  every  few  days;  it. is  well  to 
shift  them  daily  according  to  a  definite  plan.) 

Rotating  tables  built  on  motor-cycle  wheels  can  be  supplied  by 
the  Plant  World,  but  it  is  probably  best  for  each  cooperator  to 
superintend  the  building  of  his  own.  Tripod  bases  can  be  sup- 
plied at  $15.00  apiece,  just  the  casting.  Five-ply  wood  circles, 
painted,  four  feet  in  diameter,  can  be  supplied  at  $12.00  apiece, 
packing  included.  The  bearing  portion  may  be  built  of  a  bicycle 
hub,  etc.,  in  various  ways  that  will  suggest  themselves,  and 
second-hand  wheels  may  perhaps  be  obtained  in  some  places. 

20  , 


A  satisfactory  rotating  bearing  (with  an  insufficient  reducing 
gear)  is  offered  by  Winfield  H,  Smith,  Buffalo,  N.  Y.,  and  the 
table  top  may  be  attached  to  this,  which  itself  may  be  attached 
to  a  greenhouse  bench  or  other  suitable  support.  The  same  firm 
offers  an  excellent  reducing  gear  (which  is  needed  besides  the 
one  coming  with  the  bearing,  and  which  is  of  course  needed  with 
any  table  built  on  a  bicycle  wheel) .  A  finer  type  of  gear  was 
recently  supplied  by  the  Eberbach  Company,  Ann  Arbor,  Mich. 
The  electric  motor  for  this  work  should  be  of  a  rating  of  about 
14  horse-power.  It  is  to  be  remembered  that  the  motor  and 
table  operate  continuously,  night  and  day,  for  many  weeks  or 
even  months  at  a  time,  and  proper  lubrication  is  of  course 
essential. 

Records  of  Aerial  Conditions. 

The  non-solution  conditions  will  not  be  controlled  in  these 
tests;  the  complex  of  these  will  vary  from  hour  to  hour  and 
from  day  to  day  for  any  series,  and  it  will  differ  from  season  to 
season  at  the  same  station  and  from  station  to  station  at  the 
same  season.  In  order  to  secure  a  rough  description  of  this  com- 
plex for  each  experiment,  four  kinds  of  records  are  to  be  ob- 
tained. These  have  to  do  with  (1)  air  temperature,  (2)  reading 
of  white  spherical  porous-cup  atmometer,  (3)  reading  of  black 
spherical  porous-cup  atmometer,  and  (4)  duration  of  sunshine. 
Methods  for  these  records  are  set  forth  below. 

(1)  The  records  are  to  show  the  maximum  and  minimum 
air  temperature  in  shade  at  the  experiment  location  for  every  day 
of  each  experiment.  These  records  may  be  obtained  by  the  use 
of  a  max.-min.  thermometer  (read  daily  after  the  occurrence  of 
the  maximum  for  the  day) ,  or  they  may  be  taken  off  from  a  ther- 
mograph record  sheet.  The  data  are  to  appear  in  terms  of  the 
centigrade  scale. 

(2),  (3)  Standardized  black  and  white  spherical  atmometer 
cups,  with  simple  mountings,  will  be  furnished  by  the  committee 
at  cost  ($10.00  for  two  whites  and  two  blacks,  with  two  simple 
mountings) .  Orders  should  be  sent  to  Baltimore.  The  two  in- 
struments should  stand  on  the  rotating  table,  within  the  circular 
area  left  free  by  the  peripheral  row,  or  rows,  of  cultures.  They 
should  be  operated  with  distilled  water,  the  porous  surfaces 
should  be  scrubbed  with  distilled  water  and  a  tboth-brush  once 
a  week,  and  they  should  be  read  weekly,  always  at  the  same  hour 
of  the  day.  Since  water  is  apt  to  enter  the  instrument  during  the 
operation  of  scrubbing,  this  operation  should  take  place  after 

21 


the  reading  and  before  the  final  setting  of  the  instrument  for  the 
next  week's  run.  The  best  way  to  obtain  readings  is  to  weigh 
the  entire  instrument  at  the  beginning  and  end  of  each  weekly- 
run.  The  weekly  procedure  is  consequently  as  follows:  weigh 
the  instrument,  scrub  the  sphere,  wipe  off  what  water  clings  to 
tube,  stoppers  and  bottle,  add  water  to  bottle  more  than  suffi- 
cient for  the  next  run,  and  reweigh.  The  loss  in  weight  by  evapo- 
ration for  each  week  constitutes  the  weekly  reading,  and  five  of 
these  data  for  each  type  of  instrument  are  needed  for  the  five- 
week  period  of  the  seedling  phase.  These  data  will  give  evidence- 
of  the  kind  of  evaporation  and  sunshine  conditions  to  which  the 
plants  have  been  subjected. 

At  the  end  of  a  given  series  the  spheres  are  to  be  dismounted 
and  dried,  wrapped  in  paper,  and  sent  (in  a  strong  container  and 
by  parcel  post)  to  the  Laboratory  of  Plant  Physiology,  Johns 
Hopkins  University,  Homewood,  Baltimore,  Md.  They  will  be  re- 
standardized,  and  the  new  coefficients  will  be  sent  to  cooperators. 
The  spheres  will  be  returned,  or  other  ones  will  be  sent  in  their 
place  (in  case  they  seem  injured) .  (On  operation  of  porous-cup 
atmometers  see: — Livingston,  B.  E.,  Atmometry  and  the  porous- 
cup  atmometer.  Plant  World  18:  21-30,  51-74,  95-111,  143-149. 
1915.  Reprints  may  be  procured  from  the  Plant  World,  Tucson, 
Ariz.  The  second  pair  of  spheres  is  to  be  used  during  the  time 
required  for  restandardization. 

(4)  Sunshine  records  are  to  be  obtained  for  the  period  of  each 
experiment  series,  from  the  nearest  U.  S.  Weather  Bureau  Sta- 
tion operating  a  Marvin  sunshine-recorder,  these  records  being 
in  the  form  of  the  daily  duration  (hours)  of  sunshine,  as  shown 
by  that  instrument. 

THE  CULTURE  SOLUTIONS  FOR  ALL  PHASES. 

Introduction. 

It  is  obvious  that  there  are  actually  an  infinite  number  of 
different  solutions  that  must  needs  be  tested  if  we  are  to  find  out 
just  what  solution  is  the  very  best  for  a  given  plant  and  for  a 
given  growth  phase.  Of  course  our  experimentation  must  merely 
approach  finding  this  best  solution  and  it  must  proceed  by  sam- 
pling the  range  of  solution  possibilities  (or  promising  portions  of 
that  range) ,  as  it  were.  It  is  highly  desirable  that  the  sample 
solutions  be  selected,  for  the  beginning,  at  uniform  intervals 
throughout  any  promising  range  of  possibilities,  and  that  the 
intervals  be  not  so  broad  as  to  let  the  best  solution  in  the  region 
(for  which  we  are  looking)  escape  being  fairly  represented  by 

22 


one  of  the  samples  tested.  On  the  other  hand,  the  intervals  be- 
tween the  solutions  selected  for  test — out  of  the  infinite  number 
of  possible  ones —  might  be  made  so  narrow  that  the  large  num- 
ber of  tests  required  would  render  the  whole  project  hopeless. 
We  cannot  hope  to  test  millions  of  different  solutions,  nor  should 
we  hope  for  much  real  progress  if  we  were  to  test  only  a  dozen, 
for  instance.  In  arranging  the  scheme  of  solution  to  be  first 
tested,  as  presented  below,  the  judgments  of  a  number  of  spe- 
cialists in  this  general  field  have  been  combined.  It  must  be 
remembered  that  the  present  plan  does  not  pretend  to  lay  out 
the  experimentation  excepting  for  the  beginning  of  our  work. 
We  begin  by  sampling  a  certain  region  only  of  the  whole  infinite 
field  of  solution  possibilities.  Other  regions  may  be  attacked 
later. 

We  proceed  on  the  general  physiological  principle  that  the 
best  solutions  for  plant  growth  must  always  contain  at  least 
some  of  each  of  the  seven  chemical  elements  known  to  be  essen- 
tial for  all  plant  activity :  K,  Ca,  Mg,  Fe,  N,  P.  and  S.  It  appears 
safe  to  say  that  it  would  be  useless  to  test  any  solution  not  con- 
taining all  of  these  elements,  in  a  search  for  the  best  solution  for 
any  plant  and  growth  phase.  Consequently,  under  the  guidance 
of  our  present  knowledge,  we  do  not  need  to  deal  with  any  solu- 
tion that  does  not  contain  all  of  the  seven  recognized  essential 
elements  for  higher  plants  in  general. 

Furthermore,  experience  has  already  shown  that  no  solution 
may  be  expected  to  support  good  plant  growth  if  it  contains  more 
than  a  small  trace  of  iron.  On  this  account,  and  because  agri- 
culture seldom  meets  with  either  a  deficiency  or  an  excess  of  iron- 
as  a  source  of  trouble,  we  shall  at  first  make  no  study  of  different 
partial  concentrations  of  that  element.  We  shall  follow  Tot- 
tingham  in  supplying  iron  as  FePO'  in  the  same,  very  small, 
amount  to  every  solution  employed  after  the  germination  phase. 
(For  that  phase  the  suuply  of  iron  in  the  seed  may  safely  be  con- 
sidered as  sufficient.) 

It  is  of  course  logically  possible  (perhaps  even  probable)  that 
the  very  best  solution  for  any  plant  and  phase  may  eventually  be 
found  to  contain  still  other  elements  besides  the  seven  recognized 
essential  ones.  We  shall  ignore  this  proposition  at  the  beginning 
of  our  work,  however,  and  shall  study  only  solutions  containing 
just  the  six  elements  K,  Ca,  Mg,  N,  P,  and  S,  in  various  propor- 
tions and  in  various  total  concentrations,  besides  a  trace  of  Fe. 
Later  plans  will  perhaps  introduce  some  of  the  apparently  most 
promising  non-essential  elements,  such  as  Na,  CI,  Si,  Mn,  etc., 

23 


but  it  would  be  quite  hopeless  to  attempt  to  bring  these  into  con- 
sideration at  the  start,  especially  considering  the  limited  number 
of  cooperators  available.  It  should  be  remarked  that  there  will 
surely  be  a  considerable  amount  of  silicon  in  all  the  solutions 
tested  (since  uncoated  glass  containers  are  to  be  employed),  but 
the  amount  of  this  element  present  may  be  considered  as  prac- 
tically the  same  in  all  solutions.  Like  iron,  it  will  be  uniformly 
present  in  small  amount.  The  same  is  true,  to  a  degree,  of 
sodium ;  and  to  a  smaller  degree  of  chlorine.  But  the  traces  of 
these  three  elements  that  may  be  present  are  ignored  for  the 
part  of  the  project  now  being  planned. 

From  these  considerations  it  emerges  that  our  present  plans 
involve  simply  the  testing  of  solutions  containing  the  six  ele- 
ments that  are  essential  in  considerable  quantities,  with  addi- 
tion of  a  trace  of  the  seventh  essential  element,  Fe.  As  Shive 
(1915)  has  pointed  out,  the  simplest  way  to  get  these  six  ele- 
ments into  solution  is  to  prepare  the  solution  from  three  salts; 
since  three  of  the  elements  occur  as  kations  and  the  other  three 
occur  in  anions.  It  appears  best,  at  the  start,  to  employ  N  as 
the  nitrate  ion  (NOO,  P  as  the  di-hydrogen  phosphate  ion 
(H^PO*),  and  S  as  the  sulphate  ion  (SO*).  Other  carriers  of 
these  three  elements  may  be  studied  later,  such  as  nitrates,  am- 
monium salts,  mono-hydrogen  phosphates,  sulphites,  etc.  It  is 
even  probable  that  ammonium  may  need  to  be  introduced  for 
later  growth  phases  of  soy  bean  to  get  even  presentable  growth, 
but  this  matter  is  not  now  before  us. 

Of  course  it  may  be  that  no  possible  three-salt  solution  is  best 
suited  to  the  growth  of  a  given  plant  in  a  given  developmental 
phase ;  it  is  clear  that  there  are  many  sets  of  element  or  ion  pro- 
portions that  cannot  be  obtained  in  a  three-salt  solution  at  all, 
and  four-,  five-,  six-,  etc.,  salt  solutions  must  logically  be  brought 
into  the  experimental  comparison  before  the  very  best  possible 
six-ion  solution  may  be  established.  It  seems  desirable,  however, 
to  make  a  very  thorough  study  of  the  three-salt  possibilities  be- 
fore moving  forward  to  attack  the  much  more  complex  types  of 
solution  with  more  than  three  salts.  One  type  of  such  solution 
has  been  studied  by  Tottingham  (1914)  for  young  wheat  plants. 
As  our  project  goes  forward,  plans  for  later  campaigns  may  be 
formulated,  but  an  attempt  at  their  consideration  would  be  boot- 
less at  present. 

The  Three-Salt  Solutions  Characterized. 

As  Livingston  and  Tottingham  have  pointed  out  (Amer.  Jour. 
Bot.  5:  337-346.     1918.    A  reprint  may  be  obtained  from  either 

24 


author),  there  are  exactly  six  possible  types  of  three-salt  solu- 
tions that  can  be  made  to  contain  just  these  six  ions,  K,  Ca,  Mg, 
H2P0%  N0%  and  SO',  and  it  is  a  rather  thorough  test  of  these  six 
types  that  is  contemplated  for  the  first  stage  of  the  present 
project. 

It  should  be  added  that  there  are  three  other  essential  ele- 
ments, besides  the  ones  mentioned  above,  that  are  always  present 
in  any  of  these  solutions;  namely,  C,  H,  and  0.  The  solution  is 
mostly  water,  oxygen  occurs  as  a  solute  and  also  in  every  one  of 
the  three  anions  employed,  hydrogen  occurs  in  the  di-hydrogen 
phosphate  ion,  and  CO-  occurs  as  a  solute  (thus  adding  the  ele- 
ment C).  It  may  be  that  the  oxygen  atom  in  an  ion  will  prove 
to  be  negligible  in  such  work  as  this  (it  seems  not  to  have  been  given 
serious  consideration  in  any  of  the  published  discussions  of 
nutrient  solutions  and  fertilizers),  but  it  is  certain  that  the 
H-ion,  as  such,  is  of  great  importance  in  determining  the  physio- 
logical properties  of  nutrient  solutions  for  plants.  (See,  for 
example: — Sorenson,  S.  P.  L.  Ueber  die  Messung  und  Bedeu- 
tung  der  Wasserstoffionenkonzentration  bei  biologischen  Prozes- 
sen.  Ergeb.  Physiol.  .12:  393-532.  1912.  Sharp,  L.  T.,  and 
D.  R.  Hoagland.  Acidity  and  absorption  in  soils  as  measured  by 
the  hydrogen  electrode.  Jour.  Agric.  Res.  7:  123-145.  1918. 
Plummer,  J.  K.  Studies  on  soil  reaction  as  indicated  by  the 
hydrogen   electrode.     Jour.   Agric.   Res.   12:    19-31.     1918.) 

The  six  possible  types  of  three-salt  solution  are  represented 
below,  the  arrangement  being  the  same  as  that  employed  by 
Livingston  and  Tottingham  (1918).  On  the  basis  of  present 
knowledge  the  presence  of  carbon  dioxide  in  these  solutions  may 
be  ignored  as  without  significant  influence  upon  the  plants. 

I.  II.  III.  IV.  V.  VI. 

Ca(N03)t  Ca(N03)2       Ca(HaP04)3    CaCHsPOO*      CaSO*  CaSO* 

KH=PO*      K2SO1  KNOs  K2SO4  KNO.  KH^PO* 

MgSO*        Mg(H2PO*)2  MgS04  Mg(N08)»         Mg(H2PO0*  Mg(NO«)t 

Our  first  problem  is  to  find  (by  actual  test  with  each  growth 
phase)  the  best  set  of  volume-molecular  proportions  and  the 
best  total  concentration  for  each  type  of  solution.  Now,  there 
is  clearly  an  infinite  number  of  possible  sets  of  proportions  of 
any  three  things,  and  for  each  set  of  salt  proportions  of  each  of 
the  six  types  there  is  an  infinite  number  of  total  concentrations. 
We  choose,  from  the  very  large  series  of  different  sets  of  salt 

25 


proportions  possible  for  each  solution  type,  just  twenty-one; 
and  we  select  them  so  as  to  be  representative  of  the  mathematic- 
ally possible  range  of  sets  of  proportions.  This  is  accomplished 
by  letting  the  volume-molecular  partial  concentration  of  each 
salt  differ  from  solution  to  solution  (in  a  series  of  twenty-one 
solutions,  all  with  the  same  total  concentration,  measured  osmot- 
ically)  by  increments  of  one-eighth  of  the  total  volume-molecu- 
lar concentration.  Previous  workers  in  this  field  have  mainly 
used  increments  of  one-tenth,  and  have  employed  osmotic  pro- 
portions instead  of  volume-molecular  proportions.  For  each  of 
the  six  types  of  solution  (numbered  in  Roman  numerals  above) 
all  the  possible  sets  of  salt  proportions,  with  increments  of  one- 
eighth,  are  represented  by  the  points  in  a  triangular  diagram, 
as  first  used  in  this  sort  of  work  by  Schreiner  and  Skinner  (U. 
S.  Bur.  Soils,  Bull.  70,  1910.  Also  Bot.  Gaz.  50:  1-30.  1910.) 
and  later  by  Shive,  McCall,  Hibbard.  (See  Shive — 1915 — for 
the  general  plan  of  such  a  diagram,  but  it  is  to  be  remembered 
that  he  used  increments  of  one-tenth  and  thirty-six  sets  of  pro- 
portions, while  we  employ  increments  of  one-eighth  and  have 
only  twenty-one  sets.)  In  diagraming  the  solutions  for  the 
present  project  it  is  earnestly  requested  that  all  diagrams  follow 
the  same  system.  Let  the  base  line  for  the  potassium  salt  be  the 
base  of  the  triangle,  and  let  that  for  the  calcium  salt  be  the  left 
side.  The  right  side  will  then  be  the  base  line  for  the  magnesium 
salt,  Each  of  these  three  base  lines  represents  a  row  of  solu- 
tions each  having  one-eighth  of  its  total  volume-molecular  con- 
centration due  to  the  salt  for  which  the  line  is  named.  The  apex 
opposite  this  lipe  represents  a  solution  in  which  six-eighths  are 
due  to  that  salt.  The  volume-molecular  proportions  of  all  three 
salts  are  quickly  determined  for  any  solution  represented  on  the 
diagram.  The  diagram  is  given  herewith.  To  designate  the 
solutions,  the  rows  on  the 
diagram      are      numbered  R6 

from  below  upward,  and 
the  solutions  are  numbered 
in  each  row  from  left  to 
right.  To  refer  to  a  solu- 
tion we  first  write  the 
Roman  numeral  denoting 
the  type  (what  three  salts 
are  used),  then  we  write 

the  row  number  (preceded  ,  ,  ,  ,  , 

by  the  letter  R),  then  we         SI       S2       S3      S4       S5       S6 
write  the  solution  number 

26 


R5 

R4 

113 

R2 

•          • 
Rl 

in  the  row,  preceded  by  S) ,  and  finally  we  state  (in  parentheses) 
the  total  concentration,  in  terms  of  atmospheres  of  osmotic  pres- 
sure representing  the  calculated  osmotic  value  of  the  solution  in 
question.  Examples  are:— IR2S3  (1.00  atm.),  IIIR1S2  (1.50 
atm.),  VR6S1  (1.65  atm.),  etc.  This  form  of  notation  is  em- 
ployed in  the  tables  given  below,  and  it  is  hoped  that  all  coopera- 
tors  will  adhere  strictly,  in  order  to  facilitate  comparisons. 
(Previous  writers  have  employed  C  in  placer  of  S,  but  it  seems  a 
little  better  to  use  S  as  standing  for  solution  rather  than  C,  de- 
noting culture.) 

Blank  triangular  diagrams,  printed  on  sheets  SV^xll  in.,  may 
be  obtained  from  Baltimore  at  a  price  of  $1.00  per  hundred. 

Aside  from  the  kinds  of  salt  entering  into  one  of  these  solu- 
tions (solution  type)  there  are  four  characteristics  by  which 
that  solution  may  be  distinguished:  (1)  volume-molecular  salt 
proportions,  (2)  osmotic  salt  proportions  (see  Tottingham, 
1914),  (3)  total  volume-molecular  concentration  (proportional 
to  the  number  of  molecules,  of  all  kinds,  per  liter) ,  and  (4)  total 
osmotic  concentration  (taken  to  be  proportional  to  the  number 
of  particles, — molecular  groups,  molecules  and  ions,  of  all  kinds, 
— per  litre;  this  last  characteristic  may  be  expressed  in  various 
ways,  but  the  atmosphere  will  be  the  unit  here  used  as  a  measure 
of  the  calculated  osmotic  value,  or  the  calculated  potential 
osmotic  pressure  (of  which  the  solution  is  taken  to  be  capable) . 
On  account  of  ionization  (and  probably  hydration),  nos.  1  and  2 
do  not  vary  proportionally  to  each  other  from  solution  to  solu- 
tion in  our  series ;  nor  do  nos.  3  and  4.  It  follows  that  if  we  plan 
our  series  of  twenty-one  solutions  to  vary  by  definite  increments 
on  the  basis  of  no.  1  (volume-molecular  salt  proportions),  then 
they  must  vary  irregularly  in  respect  to  no.  2  (osmotic  salt  pro- 
portions). The  variation  cannot  be  regular  by  both  criteria  at 
once,  and  we  have  chosen  the  former  as  the  one  to  be  used.  This 
criterion  (no.  1)  can  be  definitely  stated  for  any  of  the  solutions 
without  any  assumption  regarding  ionization,  osmotic  phe- 
nomena, etc.  On  the  other  hand,  since  the  total  concentration 
of  a  solution  must  act  upon  plants  primarily  in  an  osmotic  way, 
the  calculated  osmotic  value  (no.  3,  above)  is  here  used  for  this 
measure  of  the  main  physical  character  of  any  solution.  This 
usage  involves  calculation,  and  assumptions  as  to  ionization,  or 
direct  measurements  of  the  lowering  of  the  freezing-point,  but 
it  seems  desirable  (at  the  start,  and  in  spite  of  uncertainties) 
to  compare  all  the  twenty-one  selected  sets  of  salt  proportions, 
keeping  the  calculated  total  osmotic  value  constant  throughout 

27 


each  series.  The  dilutions  shown  in  the  tables  given  below  are 
based  on  freezing-point  determinations  made  by  Dr.  Shive,  espe- 
cially for  this  work.  Other  plans  of  dilution  (which  cannot  alter 
the  volume-molecular  salt  proportions  in  any  given  case)  may  of 
course  be  employed.  The  osmotic  values  are  to  be  considered  as 
much  less  precise  than  the  salt  proportions. 

In  this  general  connection,  it  may  be  noted  that  actual  ionic 
partial  concentrations  of  the  various  salts  in  any  of  these  three- 
salt  solutions  is  at  present  impossible  to  determine  (with  the 
single  exception  of  the  hydrogen-ion,  for  which  a  method  is  of 
course  available) ,  and  any  mental  picture  of  assumed  values 
of  the  degrees  of  ionization  of  the  various  kinds  of  salt  molecules 
must  depend  upon  more  or  less  probable  assumptions,  for  the 
actual  testing  of  which  no  methods  have  yet  been  devised.  The 
physical  chemistry  of  such  three-salt  solutions  as  these  is  still 
far  beyond  us,  excepting  in  its  most  general  aspects.  But  physi- 
ology and  agriculture  need  not  wait  for  the  advance  of  physical 
chemistry  in  this  connection ;  we  aim  to  determine  the  physio- 
logical properties  of  our  solutions  (by  plant  tests)  and  merely  to 
define  our  solutions  in  such  a  way  that  they  may  be  reproduced 
at  any  time  in  the  future,  for  advanced  physical-chemical  study, 
etc.  Any  solution  is  sufficiently  defined  for  exact  reproduction 
when  the  volume-molecular  partial  concentration  is  stated  for 
each  of  the  salts  used. 

For  a  beginning,  we  wish  to  compare  the  twenty-one  different 
sets  of  salt  proportions  for  each  of  the  six  types  of  solution  and 
for  the  same  total  osmotic  concentration  throughout  the  entire 
series.  The  uniform  total  concentration  adopted  should  be  one 
that  promises  to  be  suitable  for  good  growth  of  the  plants,  and, 
at  the  same  time,  it  must  be  such  that  all  of  the  solutions  may  be 
possible  in  this  concentration  without  the  formation  of  precipi- 
tate. The  osmotic  value  of  1.00  atmosphere  at  25°  C.  is  chosen 
as  the  index  of  this  uniform  total  concentration.  There  are  thus 
126  different  solutions  (really  only  123,  see  below)  to  be  com- 
pared in  the  beginning,  all  having  the  same  osmotic  value  (1.00 
atm.),  but  all  differing  in  other  ways  (salt  proportions  or  kinds 
of  salts  used). 

The  formulas  for  the  126  solutions,  and  fpr  the  universal  con- 
trol solution  (Shive's  IR5C2,  increments  of  1/10,  1.75  atm.)  are 
given  in  the  accompanying  tables,  which  have  been  prepared  by 
Dr.  Shive  for  this  project.  It  will  be  noted  that  there  is  a  sepa- 
rate table  for  each  of  the  six  types  of  solution  and  that  each  table 
presents  the  twenty-one  different  sets  of  volume-molecular  salt 

28 


proportions  for  its  own  type.  In  each  table,  the  first  column 
shov/s  the  twenty-one  solution  numbers,  the  next  three  columns 
present  the  volume-molecular  proportions  of  the  three  salts  used, 
and  the  remaining  three  columns  give  the  actual  volume-molecular 
partial  concentrations  of  the  three  salts — the  latter  always  stated 
for  a  mixture  having  a  total  osmotic  value  of  1.00  atmosphere. 
The  reader  should  be  warned  that  the  relative  partial  concen- 
trations cannot  be  read  vertically ;  for  example,  in  table  I  it  can- 
not be  said  that  the  volume-molecular  partial  concentration  of 
KH-PO^  is  the  same  in  all  solutions  of  row  1,  etc.,  although  the 
relative  proportional  values  for  this  salt  are  all  set  down  as  unity 
for  these  solutions.  The  data  of  the  last  three  columns  of  the 
table  show  how  this  comes  about ;  the  unit  used  in  reckoning  the 
relative  proportions  steadily  becomes  smaller  as  we  proceed 
along  the  row  from  left  to  right  (on  the  triangular  diagram). 
This  reduction  is  necessary  on  account  of  the  phenomena  of  ioni- 
zation, etc.  (as  evidenced  when  the  complete  solutions  are  sub- 
jected to  the  freezing-point  determination),  and  on  account  of 
the  desideratum  that  all  solutions  should  have  approximately  the 
same  osmotic  value  (1.00  atm.) .  But  the  relative  salt  proportions 
for  each  individual  solution  are  stated  correctly  if  simply  read 
from  left  to  right  in  the  table;  thus,  for  IRISI,  KH^PO*: 
Ca  ( NO 0  - :  MgSO^ : :  1 : 1 : 6,  etc.  It  will  be  noted  that  the  proportions 
of  elements  and  ions  may  be  read  in  a  similar  way,  note  being 
taken  of  the  number  of  atoms  or  ions  in  each  molecule  considered. 
Thus,  K:Ca:Mg  ::  1 :1:6 ;  but  PO^:  NO^:  SO^::  1:2:6,  andH:N: 
S: :  2:2:6.  The  proportions  of  the  three  kations  K,  Ca,  and  Mg 
are  read  directly  from  the  position  of  the  solution  on  the  triangu- 
lar diagram  for  types  I,  III,  V  and  VI,  since  none  of  the  mole- 
cules used  for  these  types  gives  more  than  a  single  one  of  these 
ions.  For  the  other  two  types  it  must  be  remembered  that  there 
are  two  K  ions  in  each  molecule  of  K-SO^.  (In  this  last  considera- 
tion is  will  be  noted  that  the  term  "ionic  proportions"  refers  to 
atoms  or  atomic  groups — Ca,  POs  etc. — as  ions,  without  regard 
to  the  actual  degree  of  dissociation  of  the  corresponding  mole- 
cules. When  we  say  that  the  ionic  proportions  of  a  solution 
are: — PO*:  SO^:  NO'': :  1 :2:6,  we  merely  signify  that  these 
atomic  groups  were  placed  in  the  solution  in  these  proportions, 
not  implying  at  all  that  the  ionized  portion  alone  shows  such 
proportions.) 


29 


TABLE  I.     SOLUTIONS  OF  TYPE  L 

Partial  volume-molecular  concentrations  and  molecular  proportions  of 
KH2PO*,  Ca(N03)2,  and  MgSO*  in  21  solutions  all  having  a  calculated 
osmotic  value  of  approximately  1.00  atm.  at  25  °C.,  but  differing  (by  in- 
crements of  %  )  in  salt  proportions. 

The  highest  partial  volume-molecular  concentrations  of  the  salts  of  this 
table,  that  may  be  used  in  stock  solutions  (mixed)  without  change  in  the 
molecular  proportions,  are  obtained,  in  each  case,  by  multiplying  each  value 
given  in  the  table  by  the  factor  3.50.  One  liter  of  each  of  these  strongest 
stock  solutions,  properly  diluted  with  distilled  water,  will  make  3.50  liters 
of  nutrient  solution  with  an  osmotic  value  of  approximately  1.00  atm.  at 
25°C. 


Molecular  Proportions. 


Partial  Volume-molecular  Concentrations. 


Solution 
number. 

KH3PO4 

CaiNOs)!, 

MgSO< 

KHjPOi 

Ca(N03)j 

MgS04 

IRISI 

1 

6 

.0027 

.0027 

.0161 

S2 

2 

5 

.0025 

.0049 

.0123 

S3 

3 

4 

.0024 

.0071 

.0094 

S4 

4 

3 

.0022 

.0089 

.0067 

S5 

5 

2 

.0022 

.0108 

.0043 

S6 

6 

1 

.0020 

.0122 

.0020 

R2S1 

2 

1 

5 

.0053 

.0027 

.0132 

S2 

2 

2 

4 

.0049 

.0049 

.0099 

S3 

2 

3 

3 

.0047 

.0071 

.0071 

S4 

2 

4 

2 

.0045 

.0090 

.0045 

S5 

2 

5 

1 

.0041 

.0104 

.0021 

R3S1 

3 

1 

4 

.0076 

.0025 

.0101 

S2 

3 

2 

3 

.0072 

.0048 

.0072 

S3 

3 

3 

2 

.0068 

.0068 

.0045 

S4 

3 

4 

1 

.0065 

.0086 

.0021 

R4S1 

4 

1 

3 

.0099 

.0025 

.0074 

S2 

4 

2 

2 

.0094 

.0047 

.0047 

S3 

4 

3 

1 

.0090 

.0068 

.0022 

R5S1 

5 

1 

2 

.0123 

.0024 

.0049 

S2 

5 

2 

1 

.0118 

.0047 

.0023 

R6S1 

6 

1 

1 

.0145 

.0024 

.0024 

Control, 

Shive's 

R5C2 -(1.75  atm.)*  3.77        1.09         3.14 


.0180 


.0052 


.0150 


*  Shive's  solution  was  planned  on  the  basis  of  osmotic  proportions  and 
increments  of  1/10  of  the  total  osmotic  value,  so  that  the  molecular  pro- 
portions when  stated  as  eighths  are  not  whole  numbers.  On  the  present 
basis  Shive's  best  solution  is  described  as  IR3.77  SI. 09  (1.75  atm.),  and 
its  location  is  easily  found  on  our  triangular  diagram. 


30 


TABLE  11.     SOLUTIONS  OF  TYPE  IL 

Partial  volume-molecular  concentrations  and  molecular  proportions  of 
KzSOi,  Ca(NOs)»,  and  Mg(HsPO«)a  in  21  solutions  all  having  a  calculated 
osmotic  value  of  approximately  1.00  atm.  at  25  °C.,  but  differing  (by  in- 
crements of  %  )  in  salt  proportions. 

The  highest  partial  volume-molecular  concentrations  of  the  salts  of  this 
table,  that  may  be  used  in  stock  solutions  (mixed)  without  change  in  the 
molecular  proportions,  are  obtained,  in  each  case,  by  multiplying  each  value 
given  in  the  table  by  the  factor  3.70.  One  liter  of  each  of  these  strongest 
stock  solutions,  properly  diluted  with  distilled  water,  will  make  3.70  liters 
of  nutrient  solution  with  an  osmotic  value  of  approximately  1.00  atm.  at 
25  °C.     Instead  of  3.70,  the  factor  3.00  is  used,  however  (see  Table  VIII). 


Molecular  Proportions.         Partial  Volume-molecular  Concentrations. 


Solution 
number. 

Kj,SO«  Ca(NO,), 

Mgr(H,P04)2 

K2SO4 

Ca(N03)i, 

Mg(HjPOJ, 

RlSl 

1 

6 

.0019 

.0019 

.0118 

S2 

2 

5 

.0019 

.0039 

.0097 

S3 

3 

4 

.0019 

.0059 

.0078 

S4 

4 

3 

.0019 

.0075 

.0056 

S5 

5 

2 

.0019 

.0094 

.0037 

S6 

6 

1 

.0019 

.0116 

.0019 

R2S1 

2 

1 

5 

.0038 

.0019 

.0096 

S2 

2 

2 

4 

.0036 

.0036 

.0072 

S3 

2 

3 

3 

.0036 

.0054 

.0054 

S4 

2 

4 

2 

.0036 

.0072 

.0036 

S5 

2 

5 

1 

.0036 

.0091 

.0018 

R3S1 

3 

1 

4 

.0057 

.0019 

.0076 

S2 

3 

.  2 

3 

.0056 

.0037 

.0056 

S3 

3 

3 

2 

.0056 

.0057 

.0038 

S4 

3 

4 

1 

.0056 

<• 

.0075 

.0019 

R4S1 

4 

1 

3 

.0074 

.0018 

.0056 

S2 

4 

2 

2 

.0074 

.0037 

.0037 

S3 

4 

3 

1 

.0075 

.0056 

.0019 

R5S1 

5 

1 

2 

.0094 

.0019 

.0037 

S2 

5 

2 

1 

.0094 

.0037 

.0019 

R6S1 

6 

1 

1 

.0112 

.0019 

.0019 

Control,  Shive's 

R5C2  (1.75  atm.) 

*  3.77 

1.09 

3.14 

.0180 

.0052 

.0150 

*  See  footnote  to  Table  I. 


81 


TABLE  III.     SOLUTIONS  OF  TYPE  III. 

Partial  volume-molecular  concentrations  and  molecular  proportions  of 
KNO»,  Ca(H2P04)2,  and  MgSOi  in  21  solutions  all  having  a  calculated 
osmotic  value  of  approximately  1.00  atm.  at  25  °C.,  but  differing  (by  in- 
crements of  Vs  )  in  salt  proportions. 

The  highest  partial  volume-molecular  concentrations  of  the  salts  of  this 
table,  that  may  be  used  in  stock  solutions  (mixed)  without  change  in  the 
molecular  proportions,  are  obtained,  in  each  case,  by  multiplying  each  value 
given  in  the  table  by  the  factor  3.70  .  One  liter  of  each  of  these  strongest 
stock  solutions,  properly  diluted  with  distilled  water,  will  make  3.70  liters 
of  nutrient  solution  with  an  osmotic  value  of  approximately  1.00  atm.  at 
25  °C.    Instead  of  3.70,  the  factor  3.50  is  used,  however  (see  Table  IX). 

Molecular  Proportions.         Partial  Volume-molecular  Concentrations. 


Solution 
number. 

KNOi,  Ca(H2P04)t 

UgSOi 

KNO, 

Ca(Hi!POJi, 

MgSO* 

RlSl 

1 

6 

.0027 

.0027 

.0165 

S2 

2 

5 

.0026 

.0053 

.0132 

S3 

3 

4 

.0024 

.0073 

.0098 

S4 

4 

3 

.0023 

.0093 

.0070 

S5 

5 

2 

.0021 

.0106 

.0042 

S6 

6 

1 

.0021 

.0125 

.0021 

R2S1 

2 

1 

5 

.0054 

.0027 

.0135 

S2 

2 

2 

4 

.0048 

.0048 

.0096 

S3 

2 

3 

3 

.0045 

.0067 

.0067 

/     S4 

2 

4 

2 

.0042 

.0084 

.0042 

/     S5 

2 

5 

1 

.0041 

.0103 

.0020 

^   R3S1 

3 

1 

4 

.0075 

.0025 

.0099 

S2 

3 

2 

3 

.0070 

.0047 

.0070 

S3 

3 

3 

2 

.0067 

.0067 

.0045 

S4 

3 

4 

1 

.0064 

.0086 

.0021 

R4S1 

4 

1 

3 

.0099 

.0025 

.0074 

S2 

4 

2 

2 

.0093 

.0047 

.0047 

S3 

4 

3 

1 

.0085 

.0064 

.0021 

R5S1 

5 

1 

2 

.0125 

.  .0024 

.0048 

S2 

5 

2 

1 

.0113 

.0045 

.0023 

R6S1 

6 

1 

1 

.0139 

.0023 

.0023 

Control,  Shive's 

R5C2  (1.75  atm.) 

*  3.77 

1.09 

3.14 

.0180 

.0052 

.0150 

*  See  footnote  to  Table  I. 

82 


TABLE  IV.     SOLUTIONS  OF  TYPE  IV. 

Partial  volume-molecular  concentrations  and  molecular  proportions  of 
K2SO4,  C^(H2P04)2,  and  Mg(N03)2  in  21  solutions  all  having  a  calculated 
osmotic  value  of  approximately  1.00  atm.  at  25 °C.,  but  differing  (by  in- 
crements of  %  )  in  salt  proportions. 

The  highest  partial  volume-molecular  concentrations  of  the  salts  of  this 
table,  that  may  be  used  in  stock  solutions  (mixed)  without  change  in  the 
molecular  proportions,  are  obtained,  in  each  case,  by  multiplying  each  value 
given  in  the  table  by  the  factor  4.20.  One  liter  of  each  of  these  strongest 
stock  solutions,  properly  diluted  with  distilled  water,  will  make  4.20  liters 
of  nutrient  solution  with  an  osmotic  value  of  approximately  1.00  atm.  at 
25 °C.     Instead  of  4.20,  the  factor  3.00  is  used,  however  (see  Table  X). 


Molecular  Proportions. 


Partial  Volume-molecular  Concentrations. 


Solution 
number.  . 

RlSl 

S2 
S3 
S4 
S5 
S6 

K2SO4  Ca(HjP04)j 

1     1 
1     2 
1     3 
1     4 
1     5 
1     6 

Mgr(N03)i, 
6 
5 
4 
3 
2 
1 

K2SO4 
.0018 
.0018 
.0019 
.0019 
.0019 
.0019 

CaCHjPOi), 

.0018 
.0036 
.0056 
.0075 
.0093 
.0113 

Mg(NO,)2 

.0108 
.0092 
.0075 
.0056 
.0037 
.0019 

R2S1 

S2 
S3 
S4 
S5 

2 
2 
2 
2 
2 

1 
2 
3 
4 
5 

5 
4 
3 
2 
1 

.0037 
0.037 
.0037 
.0038 
.0038 

.0018 
.0037 
.0056 
.0077 
.0097 

.0091 
.0074 
.0056 
.0038 
.0019 

R3S1 
S2 
S3 

S4 

3 
3 
3 
3 

1 
2 
3 
4 

4 
3 
2 
1 

.0056 
.0056 
.0056 
.0057 

.0019 
.0037 
.0056 
.0075 

.0075 
.0056 
.0038 
.0019 

R4S1 
S2 
S3 

4 
4 
4 

1 
2 
3 

3 
2 

1 

.0076 
.0077 
.0078 

.0019 
.0039 
.0059 

.0057 
.0039 
.0019 

R5S1 
S2 

5 
5 

1 
2 

2 
1 

.0097 
.0098 

.0019 
.0039 

.0039 
.0019 

R6S1 

6 

1 

1 

.0116 

.0019 

.0019 

Control,  Shive's 
R5C2  (1.75  atm.) 

*  3.77 

1.09 

3.14 

.0180 

.0052 

.0150 

*  See  footnote  to  Table  I. 

33 


TABLE  V.     SOLUTIONS  OF  TYPE  V. 

Partial  volume-molecular  concentrations  and  molecular  proportions  of 
KNO3,  CaSO«,  and  Mg(H2POi)2  in  21  solutions  all  having  a  calculated 
osmotic  value  of  approximately  1.00  atm.  at  25  °C.,  but  differing  (by  in- 
crements of  %  )  in  salt  proportions. 

The  highest  partial  volume-molecular  concentrations  of  the  salts  of  this 
table,  that  may  be  employed  in  the  nutrient  solutions  of  this  series  are 
those  actually  given  here. 


Solution 
number. 

KNO« 

RlSl 

S2 

S3 

S4 

S5 

[S6* 

R2S1 

2 

S2 

2 

S3 

2 

S4 

2 

S5 

2 

R3S1 

3 

S2 

3 

S3 

3 

S4 

3 

R4S1 

.  4 

S2 

4 

S3 

4 

R5S1 

5 

S2 

5 

R6S1 

6 

Control, 

Shive's 

R5C2(1.75atm.) 

**3.77 

Molecular  Proportions. 


Partial  Volume-molecular  Concentrations. 


GaSO^  MgCHaPO^j 


1.09 


3.14 


KN03 

CaSOi 

Mg(H2P04), 

.0019 

.0019 

.0115 

.0021 

.0041 

.0103 

.0021 

.0061 

.0081 

.0021 

.0088 

.0067 

.0023 

.0104 

.0041 

.0024 

.0143 

.0024] 

.0041 

.0021 

.0104 

.0042 

.0042 

.0083 

.0044 

.0067 

.0067 

.0043 

.0085 

.0043 

.0048 

.0121 

.0025 

.0065 

.0023 

.0086 

.0066 

.0044 

.0066 

.0072 

.0072 

.0048 

.0074 

.0098 

.0025 

.0086 

.0022 

.0065 

.0091 

.0046 

.0046 

.0094 

.0071 

.0024 

.0112 

.0023 

.0045 

.0113 

.0045 

.0023 

.0139 


.0180 


.0024 


.0052 


.0024 


.0150 


*  The  solubility  of  CaS04,  2H2O  is  approximately  .0140  m.   Solution  R1S6 
is  therefore  not  possible  with  an  osmotic  value  of  1.00  atm. 
**  See  footnote  to  Table  I. 


34 


TABLE  VI.     SOLUTIONS  OF  TYPE  VI. 

Partial  volume-molecular  concentrations  and  molecular  proportions  of 
KH2PO4,  CaSO«  and  Mg(N0»)2  in  21  solutions  all  having  a  calculated 
osmotic  value  of  approximately  1.00  atm.  at  25 °C.,  but  differing  (by  in- 
crements of  Vs  )  in  salt  proportions. 

The  highest  partial  volume-molecular  concentrations  of  the  salts  of  this 
table,  that  may  be  employed  in  the  nutrient  solutions  of  this  series  are 
those  actually  given  here. 


Molecular  Proportions. 


Partial  Volume-molecular  Concentrations. 


Solution 
number. 

KH0PO4 

CaSOi 

Mk(N03)2 

KH2P0* 

CaSOi 

Mg(N03)2 

RlSl 

1 

6 

.0020 

.0020 

.0116 

S2 

2 

5 

.0021 

.0041 

.0102 

S3 

1 

3 

4 

.0022 

.0065 

.0086 

S4 

4 

3 

.0023 

.0091 

.0069 

S5 

5 

2 

.0024 

.0120 

.0048 

[S6* 

6 

1 

.0026 

.0155 

.0026] 

R2S1 

2 

1 

5 

.0040 

.0021 

.0101 

S2 

2 

2 

4 

.0044 

.0044 

.0087 

S3 

2 

3 

3 

.0050 

.0070 

.0070 

S4 

2 

4 

2 

.0053 

.0107 

.0053 

[S5* 

2 

5 

1 

.0054 

.0136 

.0028] 

R3S1 

3 

1 

4 

.0062 

.0021 

.0082 

S2 

3 

2 

3 

.0068 

.0045 

.0068 

S3 

3 

3 

2 

.0073 

.0073 

.0048 

S4 

3 

4 

1 

.0079 

.0104 

.0027 

R4S1 

4 

1 

3 

.0089 

.0023 

.0067 

S2 

4 

2 

2 

.0093 

.0047 

.0047 

S3 

4 

3 

1 

.0103 

.0078 

.0026 

R5S1 

5 

1 

2 

.0120 

.0024 

.0048 

S2 

5 

2 

1 

.0130 

.0052 

.0027 

R6S1 

6 

1 

1 

.0146 

.0025 

.0025 

Control, 

Shive's 

R5C2(1. 

75atm.)**3.77 

1.09 

3.14 

.0180 

.0052 

.0150 

*The  solubility  of  CaSO*,  2H2O  is  approximately  .0140  m.   Solutions  R1S6 
and  R2S5  are  therefore  not  possible  with  an  osmotic  value  of  1.00  atm.         « 
**  See  footnote  to  Table  I. 


35 


Preparation  of  the  Solutions. 

Introduction.  The  Baker  Chemical  Company,  of  Phillipsburg, 
N.  J.,  has  very  kindly  agreed  to  prepare  the  salts  needed  for 
this  cooperation  in  special  lots,  and  at  cost,  so  that  all  of  any 
given  salt  will  be  of  the  same  lot.  These  salts  will  be  put  up  in 
sealed  bottles  with  a  label  to  indicate  this  project  of  the  National 
Research  Council,  and  the  analysis  (including  the  mean  water 
content)  will  be  shown  on  the  label.  These  salts  may  be  obtained 
from  the  above-named  manufacturers  by  specifying  that  they  are 
needed  for  the  Plant  Nutrition  Project  of  the  National  Research 
Council.  At  the  outset  of  our  work  salts  from  othefr  lots  will 
have  to  be  used,  since  it  will  take  some  time  for  the  various 
laboratories  in  this  cooperation  to  obtain  the  special  salts. 
Orders  should"  be  placed  as  soon  as  possible,  and  it  will  help  the 
work  if  the  committee  is  informed  by  sending  to  Baltimore  a 
memorandum  of  the  salts  ordered  when  the  order  is  sent  to  the 
manufacturer.     Cooperators  are  asked  to  do  this. 

The  nutrient  solutions  are  to  be  prepared  by  adding,  in  each 
case,  measured  amounts  of  the  single-salt  stock  solutions  to  a 
measured  amount  of  distilled  water.  The  first  operation  is,  con- 
sequently, to  make  up  the  single-salt  'stock  solutions. 

The  Single-Salt  Stock  Solutions.  These  should  be  made  up  so 
as  to  have  the  following  volume-molecular  concentrations.  They 
will  keep  for  a  long  time  and  should  be  tightly  stoppered  and 
preserved  in  darkness. 


KNO., 

.  1.00  vol.-mol. 

CaSOi.   2H.0, 

..  0.013  vol.-mol 

KH2PO4, 

.  0.10  vol.-mol. 

Mg(N03)..  6H2O,  . 

.  .  1.00    vol.-mol 

K2SO., 

.  1.00  vol.-mol. 

Mg(H=P04)2, 

.    0.10    vol.-mol 

Ca(N03)2,  4H2O,      . 

.  1.00  vol.-mol. 

MgSOi.  7H.0, 

.  .  1.00    vol.-mol 

Ca(H2PO0^-, 

.  0.40  vol.-mol. 

The  amount  of  salt  to  be  used  is  weighed  out  and  placed  in  dis- 
tilled water  in  a  volumetric  flask  or  other  suitable  container, 
being  shaken  from  time  to  time  until  solution  is  complete  after 
which  the  solution  is  made  up  to  required  volume  by  adding  water. 
Heat  may  be  applied  to  hasten  solution  in  some  cases,  but  it 
would  produce  decomposition  in  others.  It  is  best  to  dissolve  all 
salts  at  room  temperature,  excepting  those  noted  below,  for 
which  lower  temperature  is  needed. 

The  three  phosphates  should  be  dissolved  at  temperatures 
below  20°  C,  and  calcium  sulphate  would  be  dissolved  at  a 
temperature  below  15°   C.     Its  solubility  limit  is  lower  with 

36 


higher  temperature  and  the  concentration  required  (0.013  vol.- 
raol.)  is  almost  at  the  limit  for  ordinary  temperatures.  If  the 
larger  crystals  that  are  left  when  solution  is  nearly  complete 
are  crushed  with  a  glass  rod  the  completion  of  the  operation  is 
hastened. 

It  is  well  to  have  a  chemical  determination  (analysis  for  one 
element)  made  of  each  single-salt  stock  solution  (or  at  least  of 
the  first  lot  of  solution  made  from  a  given  bottle  of  salt)  so  as  to 
determine  whether  the  concentration  called  for  is  actually 
attained. 

The  Mixed  Stock  Solutions  and  the  Nutrient  Solutions  Them- 
selves. To  prepare  any  mixed  stock  solution,  find  the  three  par- 
tial molecular  salt  concentrations  for  that  particular  solution 
(tables  I-VI)  and  multiply  each  of  these  three  values  by  the 
factor  given  for  this  purpose.  This  factor  is  unity  for  solution 
types  V  and  VI ;  it  is  3.50  for  types  I  and  III,  and  3.0  for  types 
II  and  IV.  From  the  three  values  thus  obtained  (and  from  the 
molecular  concentration  of  each  of  the  three  corresponding 
single-salt  solutions)  calculate  the  number  of  cubic  centimeters 
of  each  single-salt  stock  solution  needed  for  making  a  liter  of  the 
mixed  stock  solution  in  question  (or  several  liters;  for  simplicity 
these  directions  are  made  to  read  for  a  single  liter).  Add  the 
three  numbers  thus  secured  and  subtract  the  sum  from  1000, 
to  give  the  number  of  cubic  centimeters  of  water  required.  Place 
this  amount  of  water  in  a  suitable  bottle  and  proceed  to  add  the 
proper  amount  of  each  ol  the  three  single-salt  solutions,  begin- 
ning with  the  least  concentrated  of  these  and  ending  with  the 
most  concentrated,  and  shake  thoroughly  to  insure  mixing  as 
thiS  liquid  runs  in  from  the  burette.  Of  course  other  procedures 
may  be  followed;  this  one  is  simple  and  requires  no  large  volu- 
metric flasks,  but  it  does  require  the  careful  measuring  of  the 
three  single-salt  solutions  and  of  the  water.  Throughout  all 
making  of  solutions  it  will  be  well  to  estimate  the  range  of  error 
introduced  and  to  keep  record  of  this  for  each  step  of  the  pro- 
ceeding. (Thus,  1  cc.  as  actually  used  may  be,  perhaps,  anything 
between  0.98  and  1.02  cc,  etc.  This  error  will  of  course  depend 
upon  the  burettes  used,  the  temperature  variations,  the  care 
exercised  by  the  operator,  etc.) 

It  will  be  noted  that  the  mixed  stock  solutions  are  more  con- 
centrated than  the  corresponding  nutrient  solutions  themselves 
(as  prepared  to  have  osmotic  values  of  1.00  atm.),  excepting  for 
types  V  and  VI.  In  these  two  cases  the  mixed  stock  solutions  are 
the  1.00-atm.  nutrient  solutions  themselves. 

37 


All  stock  solutions  are  to  be  preserved,  tightly  stoppered,  in 
darkness.  The  nutrient  solutions  to  be  actually  employed  in  the 
cultures  are  to  be  prepared,  with  proper  dilution,  from  these 
mixed  stock  solutions.  The  nutrient  solutions  may,  of  course, 
have  any  calculated  osmostic  value  below  that  of  the  mixed  stock 
solution.  It  is  planned  to  begin  the  work  using  calculated  osmotic 
values  of  1.0  atm.  for  all  solutions  and  the  data  of  tables  I-VI  all 
refer  to  this  value.  The  nutrient  solutions  themselves  may  be 
preserved,  tightly  stoppered,  in  darkness  (to  prevent  algal 
growth,  etc.),  but  it  is  undesirable  to  keep  them  too  long,  since 
alterations  might  possibly  occur.  It  seems  safe  to  preserve 
them  as  long  as  five  or  six  weeks,  but  a  more  frequent  prepara- 
tion of  new  ones  is  probably  desirable.  There  seems  to  be  no 
doubt  that  the  stronger  mixed  stock  solutions  (types  I-IV) 
will  keep  indefinitely  in  darkness,  as  will  also  the  single-salt 
stock  solutions.  If  solutions  are  preserved  for  very  long  periods 
the  solubility  of  the  glass  of  the  containers  may  become  a  consid- 
erable feature.  If  the  bottles  are  internally  paraffined  this  pos- 
sibility is  largely  removed. 

Supplementary  Tables.  Tables  VII-XII  give  the  amounts  of 
water  and  of  each  of  the  requisite  single-salt  stock  solutions  that 
are  needed  to  make  a  liter  of  each  of  the  most  concentrated 
nutrient  solutions  for  each  of  the  six  different  solution  types. 
For  example,  solution  IRISI  (table  VII)  is  made  by  placing 
924.7  cc.  of  water  in  a  suitable  container  and  then  adding  to  it, 
with  shaking,  first  9.45  cc.  of  molecular  KH^POs  then  9.45  cc. 
of  molecular  Ca(N03)^  and  finally  56.4  cc.  of  molecular  MgSO^ 
Of  course  every  single-salt  stock  solution  is  always  employed 
with  the  concentration  shown  in  parentheses  below  the  formula 
for  that  salt  in  these  tables.  (See  page  36  of  this  Plan.)  The 
stock  nutrient  solutions  of  types  V  and  VI  have  an  osmotic  value 
of  1.0  atmosphere,  while  those  of  types  I-IV  are  more  concen- 
trated. The  solutions  of  types  V  and  VI  cannot  be  generally 
made  with  higher  concentrations  than  this  value  of  1.00  atm. 
From  tables  VII-X  and  from  page  36  it  is  clear  that  the  stock 
nutrient  solutions  of  types  I  and  III  are  planned  to  be  made  3.5 
times — and  those  of  types  II  and  IV  3.0  times — as  concentrated 
as  will  be  needed  for  solutions  having  an  osmotic  value  of  1.00 
atmosphere.  Of  course  other  procedures  may  be  followed  in 
making  the  nutrient  solutions  actually  used,  but  this  plan  sup- 
poses that  the  stock  nutrient  solutions  will  be  prepared  as  here 
set  forth,  using  the  factor  1.0  for  types  V  and  VI,  3.5  for  types 
I  and  III,  and  3.0  for  types  II  and  IV.     (See  p.  37  of  this  Plan.) 

Solutions  VR1S6,  VIR1S8,  and  VIR2S5  are  not  possible  with 
an  osmotic  value  of  1.00  atm.;  they  cannot  be  tested  except  in 
series  having  a  lower  total  concentration  than  this. 

38 


TABLE  VII. 

Supplementary  for  Solutions  of  Type  I. 

Volumes  (cubic  centimeters)  of  distilled  water  and  of  the  single-salt 
stock  solutions  required  to  make  one  liter  of  each  concentrated  stock  nu- 
trient solution  of  type  I.  The  stock  nutrient  solutions  thus  made  are  each 
3.5  times  as  concentrated  as  the  corresponding  nutrient  solution  having  an 
osmotic  value  of  1.00  atmosphere. 


Solution 
number. 

H.O 

KH2PO4 

(l.Om.) 

Ca(N03)ii 
(l.Om.) 

MgSOt 

(l.Om.) 

IRISI 

924.7 

9.45 

9.45 

56.4 

S2 

931.1 

8.75 

17.15 

43.0 

S3 

935.85 

8.4 

24.85 

32.9 

S4 

937.7 

7.7 

31.15 

23.45 

S5 

939.45 

7.7 

37.8 

15.05 

S6 

943.3 

7.0 

42.7 

7.0 

R2S1 

925.8 

18.55 

9.45 

46.2 

S2 

931.05 

17.15 

17.15 

34.65 

S3 

933.85 

16.45 

24.85 

24.85 

S4 

937.0 

15.75 

31.50 

15.75 

S5 

941.9 

i    14.35 

36.4 

7.35 

R3S1 

929.3 

26.6 

8.75 

35.35 

S2 

932.8 

25.2 

16.80 

25.20 

S3 

936.55 

23.8 

23.80 

15.75 

S4 

939.80 

22,75 

30.10 

7.35 

R4S1 

930.7 

34.65   . 

8.75 

25.9 

S2 

934.2 

32.9 

16.45 

16.45 

S3 

937.0 

31.50 

23.80 

7.7 

R5S1 

931.4 

43.05 

8.4 

17.15 

S2 

934.2 

41.3 

16.45 

8.05 

R6S1  932.45  50.75  8.4  8.4 

Control, 

R3.77S1.09 

(1.75  atm.)  961.8  18.0  5.2  15.0 


39 


TYPE  VIII. 

Supplementary  for  Solutions  of  Type  11. 

Volumes  (cubic  centimeters)  of  distilled  water  and  of  the  single-salt 
stock  solutions  required  to  make  one  liter  of  each  concentrated  stock  nu- 
trient solution  of  type  II.  The  stock  nutrient  solutions  thus  made  are  3.0 
times  as  concentrated  as  the  corresponding  nutrient  solution  having  an 
osmotic  value  of  1.00  atmosphere. 


Solution 
number. 

HaO 

KsSOi 

(0.4m.) 

Ca(N03)2 
(1.0m.) 

Mg(Hi,POJ, 

(0.1m.) 

IIRISI 

626.05 

14.25 

5.7 

354.0 

S2 

683.05 

14.25 

11.7 

.  291.0 

S3 

734.05 

14.25 

17.7 

234.0 

S4 

795.25 

14.25 

22.5 

168.0 

S5 

846.55 

14.25 

28.2 

111.0 

S6 

893.95 

14.25 

34.8 

57.0 

R2S1 

677.8 

28.5 

5.7 

288.0 

S2 

746.2 

27.0 

10.8 

216.0 

S3 

794.8 

27.0 

16.2 

162.0 

S4 

843.4 

27.0 

21.6 

108.0 

S5 

891.7 

27.0 

27.3 

54.0 

R3S1 

723.55 

42.75 

5.7 

228.0 

S2 

778.9 

42.0 

11.1 

168.0 

S3 

826.9 

42.0 

17.1 

114.0 

S4 

878.5 

42.0 

22.5 

57.0 

R4S1 

771.1 

55.5 

5.4 

168.0 

S2 

822.4 

55.5 

11.1 

111.0 

S3 

869.95 

56.25 

16.8 

57.0 

R5S1 

812.8 

70.5 

5.7 

111.0 

S2 

862.2 

70.5   ' 

11.1 

57.0 

R6S1  853.3  84.0  5.7  57.0 

Control, 

R3.77S1.09 

(1.75  atm.)  961.8  18.0  5.2  15.0 


40 


TABLE  IX. 

Supplementary  for  Solutions  of  Type  III. 

Volumes  (cubic  centimeters)  of  distilled  water  and  of  the  single-salt 
stock  solutions  required  to  make  one  liter  of  each  concentrated  stock  nu- 
trient solution  of  type  III.  The  stock  nutrient  solutions  thus  made  are  each 
3.5  times  as  concentrated  as  the  corresponding  nutrient  solution  having  an 
osmotic  value  of  1.00  atmosphere. 


Solution 
number. 

H,0 

KNOj 
(l.Om.) 

CaCHsPOJ, 
(0.1m.) 

MgrS04 
(l.Om.) 

IIIRISI 

838.3 

9.45 

94.5 

57.75 

S2 

759.2 

9.1 

185.5 

46.2 

S3 

701.8 

8.4 

255.5 

34.3 

S4 

642.9 

8.05 

325.5 

24.50 

S5 

606.8 

7.35 

371.1 

14.70 

S6 

547.8 

7.35 

437.5 

7.35 

R2S1 

839.3 

18.90 

94.5 

47.25 

S2 

781.6 

16.80 

168.0 

33.60 

S3 

726.3 

15.75 

234.5 

23.45 

S4 

675.6 

14.70 

294.0 

14.70 

S5 

618. 

14.35 

360.6 

7.00 

R3S1 

851.5 

26.25 

87.5 

34.7 

S2 

786.5 

24.50 

164.5 

24.5 

S3 

726.3 

23.45 

234.5 

15.75 

S4 

669.2 

22.40 

301.0 

7.35 

R4S1 

851.9 

34.7 

87.5 

25.9 

S2 

786.5 

32.55 

164.5 

16.45 

S3 

738.9          ^ 

29.75 

224.0 

7.35 

R5S1 

855.4 

43.75 

84.0 

16.80 

S2 

794.9 

39.55 

157.5 

8.05 

R6S1 

862.8 

48.65 

80.5 

8.05 

Control, 

,  • 

R3.77S1.09 

(1.75  atm.) 

961.8 

18.0 

5.2 

15.0 

41 


TABLE  X. 

Supplementary  for  Solutions  of  Type  IV. 

Volumes  (cubic  centimeters)  of  distilled  water  and  of  the  single-salt 
stock  solutions  required  to  make  one  liter  of  each  concentrated  stock  nu- 
trient solution  of  type  IV.  The  stock  nutrient  solutions  thus  made  are  each 
3.0  times  as  concentrated  as  the  corresponding  nutrient  solution  having  an 
osmotic  value  of  1.00  atmosphere. 


Solution 
number. 

H2O 

KoSOi 
(0.4m.) 

Ca(H2P04)2 
(0.1m.) 

Mg(N03)a 
(1.0m.) 

IVRISI 

900.1 

13.5 

54.0 

32.4 

S2 

850.9 

13.5 

108.0 

27.6 

S3 

795.25 

14.25 

168.0 

22.5 

S4 

743.95 

14.25 

225.0 

16.8 

S5 

695.75 

14.25 

279.0 

11.1 

S6 

642.05 

14.25 

339.0 

5.7 

R2S1 

892.45 

26.25 

54.0 

27.3 

S2 

840.55 

26.25 

111.0 

22.2 

S3 

788.95 

26.25 

168.0 

16.8 

S4 

729.1 

28.5 

231.0 

11.4 

S5 

674.8 

28.5 

291.0 

.  5.7 

1 

R3S1 

878.5 

42.0 

57.0 

22.5 

S2 

830.2 

42.0 

111.0 

16.8 

S3 

778.6 

42.0 

168.0 

11.4 

S4 

726.6 

42.7 

225.0 

5.7 

R4S1 

868.9 

57.0 

57.0 

17.1 

.       S2 

813.5 

57.8 

117.0 

11.7 

S3 

758.8 

58.5 

177.0 

5.7 

R5S1 

858.6 

72.7 

57.0 

11.7 

S2 

803.8 

73.5 

117.0 

5.7 

R6S1 

849.6 

87.0 

57.0 

5.7 

Control, 

»» 

''\ 

R3.77S1.09 

(1.75  atm.) 

961.8 

is.o 

5.2 

15.0 

i2 


TABLE  XI. 
'   Supplementary  for  Solutions  of  Type  V. 

Volumes  (cubic  centimeters)  of  distilled  water  and  of  the  single-salt 
stock  solutions  required  to  make  one  liter  of  each  nutrient  solution  of 
type  V,  with  an  osmotic  value  of  1.00  atmosphere. 

KNO3  CaSOi  Mg(H2P04)2 

(1.0m.)  (O.aiSm.)  (0.1m.) 

1.9  146.2  115.0 

2.1  315.4  103.0 

2.1  469.2  81.0 

2.1  676.9  67.0 

2.3  800.0  41.0 

2.4  1100.0          '  24.0] 

4.1  161.5  104.0 
/  4.2  33.0.0  83.0 

4.3  515.4  67.0 

4.4  653.8  43.0 
4.8  930.8  25.0 

6.5  176.9  86.0 

6.6  338.4  66.0 

7.2  553.8  48.0 
7.4  753.8  25.0 

8.6  169.2  65.0 

9.1  353.8  46.0 

9.4  546.1  24.0 

11.2  176.9  45.0 

11.3  346.1  23.0 

13.9  184.6  24.0 


18.0  5.2  15.0 

*  Solution  VR1S6  cannot  be  made  with  a  total  concentration  value  of 
1.0  atm. 


Solution 

number. 

H2O 

VRISI 

736.9 

S2 

579.6 

S3 

447.7 

S4 

254.0 

S5 

156.7 

[S6* 

R2S1 

73*0.4 

•      S2 

582.8 

S3 

413.3 

S4 

298.8 

S5 

39.4 

R3S1 

730.6 

S2 

589.0 

S3 

391.0 

S4 

214.3 

R4S1 

757.2 

S2 

591.1 

S3 

420.5 

R5S1 

766.9 

S2 

619.6 

R6S1 

777.5 

Control, 

R3.77S1.09 

(1.75  atm.) 

961.8 

43 


TABLE  XIL 

Supplementary  foi-  Solutions  of  Type  VI. 

Volumes  (cubic  centimeters)  of  distilled  water  and  of  the  single-salt 
stock  solutions  required  to  make  one  liter  of  each  nutrient  solution  of 
type  VI,  with  an  osmotic  value  of  1.00  atmosphere. 


Solution 
number. 

HjO 

KHzPOi 
(1.0m.) 

CaSOi 
(0.013m.) 

Mk(N08) 
(1.0m.) 

VIRISI 

832.6 

2.0 

153.8 

11.6 

S2 

672.3 

2.1 

315.4 

10.2 

S3 

489.2 

2.2 

500.0 

8.6 

S4 

290.8 

2.3 

700.0 

6.9 

S5 

69.7 

2.4 

923.1 

4.8 

[S6* 

2.6 

1192.3 

2.6] 

R2S1 

824.4 

4.0 

161.5 

10.1 

S2 

648.5 

4.4 

338.4 

8.7  • 

S3 

450.0 

4.6 

538.4 

7.0 

S4 

166.3 

5.3 

823.1 

5.3 

[S5* 

5.4 

1046.1 

2.8] 

R3S1 

824.1 

6.2 

161.5 

8.2 

S2 

640.3 

6.8 

346.1 

6.8 

S3 

426.5 

7.3 

561.4 

4.8 

S4 

189.4 

7.9 

800.0 

2.7 

R4S1 

807.5 

8.9 

176.9 

6.7 

S2 

624.5 

9.3 

361.5 

4.7 

S3 

387.1 

10.3 

600.0 

2.6 

R5S1 

798.6 

12.0 

184.6 

4.8 

S2 

584:3 

13.0 

400.0 

2.7 

R6S1 

790.6 

14.6 

192.3 

2.5 

Control, 

R3.77S1.09 

-' 

(1.7.5  atm.) 

961.8 

18.0 

5.2 

15.0 

*  Solutions  VIR1S6  and  VIR2S5  cannot  be  made  with  a  total  concentra- 
tion value  of  1.0  atm. 


44 


Iron  in  the  Nutrient  Solutions.  The  source  of  iron  is  -to  be 
added  (as  ferric  phosphate)  to  each  nutrient  solution  after  it  has 
been  placed  in  the  culture  jar,  in  every  case.  The  bottle  contain- 
ing this  phosphate  is  first  to  be  thoroughly  shaken,  so  as  to  fur- 
nish a  uniform  suspension,  and  then  a  sufficient  amount  of  the 
suspension  is  to  be  transferred  to  the  culture  jar  (with  a  1-cc. 
pipette) ,  so  as  to  add  approximately  thr-ee  mg.  of  the  precipitate 
to  each  quart  jar.  After  this  addition  the  jars  are  ready  for  the 
plants. 

The  preparation  of  the  precipitated  FePO*  should  proceed  as 
follows :  In  a  bottle  with  capacity  of  2  liters  or  more  place  500 
cc.  of  a  0.04  vol.-mol.  solution  of  KH=PO^  and  add  thereto,  with 
agitation,  a  weak  solution  of  ferric  nitrate  [Fe(N08)''],  continu- 
ing the  addition  until  no  more  precipitate  is  produced.  There 
should  thus  be  formed  about  0.02  gram-molecule  of  FePOs  which 
should  remain  in  suspension  for  considerable  time,  eventually 
settling  to  the  bottom  of  the  bottle. 

Now  fill  the  bottle  nearly  full  of  distilled  water,  shake  thor- 
oughly and  stand  aside  till  nearly  all  the  liquid  is  clear.  Carefully 
siphon  off  the  clear  liquid  without  loss  of  the  precipitate,  and 
repeat  the  filling,  shaking,  settling  and  decanting  process  several 
times,  to  wash  the  FePO^  free  from  KNO-'  and  any  excess  of 
Fe(NO0'  that  was  originally  added.  The  washing  should  be 
thorough,  so  that  1  cc.  of  the  wash-water,  evaporated  at  from 
50°  to  60°  C,  in  a  porcelain  dish,  shows  no  residue.  Now  trans- 
fer all  the  precipitate,  with  its  water,  to  a  graduated  liter-flask 
and  add  distilled  water  to  make  a  liter.  Preserve  in  a  tiglitly 
stoppered  bottle.  When  shaken  thoroughly  the  suspension  thus 
formed  should  contain  approximately  0.02  g.-mol.  of  FePO*, 
about  3  g.  per  liter,  or  3  mg.  per  cubic  centimeter.  It  will  be  well 
to  prepare  enough  FePO*  to  last  for  a  year  or  two  of  this  work. 

Enough  of  the  uniform  suspension  is  to  be  added  to  each  quart 
jar  at  each  filling  to  give  3  mg.  of  FePO*.  Of  course  it  will  not 
dissolve  appreciably,  but  it  will  furnish  a  constant  and  adequate 
supply  of  iron.  This  material  is  not  to  be  added  to  the  germina- 
tion solution,  however,  as  has  been  said. 

Repetitions  of  the  Experiments.  It  is  planned  that  all  of  the 
sets  of  salt  proportions  (excepting  the  three  that  are  impossible 
with  that  concentration)  will  be  tested  at  least  once  with  an 
osmostic  value  of  1.00  atm.  The  tests  are  to  be  carried  out  by 
solution  types,  so  that  different  cooperators  may  be  working 
with  different  types  at  the  same  time.  The  prehminary  experi- 
mentation for  any  cooperator  may  thus  consist  in  the  testing  of 

45 


one  set  of  19,  20  or  21  cultures  (and  the  triplicate  control) ,  As 
soon  as  a  type  group  has  been  tested  once,  the  best  seven  solu- 
tions are  to  be  selected,  and  all  future  work  in  this  part  of  this 
project  is  to  be  confined  to  these  best  seven  sets  of  salt  propor- 
tions. This  feature  of  the  plan  soon  eliminates  two-thirds  of 
the  solutions,  and  it  is  based  on  the  assumption  that  the  best 
seven  solutions  in  any  experiment  will  probably  include  the  single 
very  best  solution  of  that  type  in  any  other  experiment,  no  mat- 
ter when  or  where  such  other  experiment  may  be  carried  out. 
While  climatic  conditions  may  shift  the  position  of  the  best  physi- 
ological balance  of  the  entire  group  in  the  series  of  the  best 
seven  sets  of  salt  proportions,  it  is  at  least  improbable  that  they 
will  shift  this  position  to  one  outside  of  this  series  of  seven.  If 
it  should  develop  that  none  of  the  solutions  of  some  type  give 
even  fair  growth— as  compared  to  the  control — then  the  whole 
of  that  type  may  be  eliminated.  It  is  thus  seen  that  the  repeti- 
tion will  deal  with  at  most  no  more  than  forty-two  different  sets 
of  salt  proportions.  These  repetitions  are  to  be  carried  out  re- 
peatedly and  under  a  great  variety  of  climatic  complexes,  and  it 
is  really  with  these  forty-two  (or  fewer)  sets  of  salt  proportions 
that  the  present  phase  of  our  campaign  is  to  deal. . 

When  the  repetitions  are  taken  up,  other  total  concentrations 
are  to  be  introduced,  besides  the  one  having  an  osmotic  value  of 
1.00  atm.  Detailed  plans  in  this  connection  may  be  postponed 
till  later,  however.  Plans  for  dealing  with  various  logically 
possible  complications  in  other  aspects  of  the  research  may  also 
be  deferred  till  such  complications  actually  arise  from  experi- 
mental results. 

SAND-CULTURES  OF  WHEAT. 

Introduction.  The  sand-culture  method  to  be  used  is  essen- 
tially that  described  by  McCall  (1916).  The  important  feature 
is  that  the  nutrient  solution  is  renewed  at  frequent  intervals,  in 
much  the  same  way  as  with  water-cultures.  As  in  all  experi- 
mentation of  this  cooperation,  it  is  necessary  that  essential  de- 
tails be  alike  in  all  experiments  if  the  results  are  to  be  com- 
parable. The  nutrient  solutions  to  be  used  are  the  same  as  those 
for  water-cultures,  so  that  there  are  one  hundred  and  twenty-six 
different  sets  of  salt  proportions  in  sand-cultures  to  be  compared, 
besides  the  general  control,  with  Shive's  solution  IR5C2  (1/10- 
increments,  1.75  atm.).  This  last  is  our  solution  IR3.77S1.09 
(see  table  I).  The  following  plan  is  based  on  a  memorandum 
furnished  the  committee  by  Dr.  McCall  and  Dr.  Shive. 

46 


Sand.  The  sand  to  be  employed  should  be  as  nearly  like  that 
used  by  McCall  as  is  possible.  (A  sample  may  be  obtained  from 
Dr.  A.  G.  McCall,  Maryland  Agric.  Exp.  Sta.,  College  Park,  Md.) 
This  sand  shows  about  98  per  cent,  of  SiO^  The  grains  are  not 
much  rounded  (artificially  crushed  quartz  should  not  be  used 
in  the  present  cooperation  nor  should  thoroughly  rounded  sand 
be  used) .  The  mechanical  analysis  (by  sieves)  shows  the  follow- 
ing proportions  as  to  diameters  of  particles:  1.0  to  0.5  mm., 
1.4  per  cent.;  0.5  to  0.25  mm.,  86.4  per  cent.;  0.25  to  0.10  mm., 
11.5  per  cent.;  0.10  to  0.05  mm.,  0.7  per  cent.  It  has  a  water- 
holding  capacity  of  31  per  cent.,  on  the  dry-weight  basis  (Hilgard 
method,  with  a  column  one  cm.  high.  (See  Hilgard,  Soils,  page 
209).  It  should  be  remembered  that  the  washing  process  re- 
moves much  of  the  most  finely-divided  material,  so  that  the  data 
just  given  are  applicable  to  the  sand  after  washing.  A  sand  that 
does  not  satisfy  these  requirements  may  be  corrected  by  addition 
or  removal  of  proper  amounts  of  certain  groups  of  particles 
(using  sieves).  The  water-holding  capacity  should  agree  with 
that  stated  above,  within  a  range  of  plus  or  minus  one  per  cent. ; 
that  is,  it  may  have  any  value  between  thirty  and  thirty-two  per 
cent,  (dry-weight  basis). 

Before  using,  the  sand  is  to  be  thoroughly  washed,  with  tap  or' 
well  water  and  then  with  distilled  water.  Washing  is  to  be  accom- 
plished as  follows:  Fill  a  large  glazed  crock  (about  five-gallon 
capacity)  about  two  thirds  full  of  water  and  pour  sand  into  this, 
stirring  vigorously  until  crock  is  about  two-thirds  full  of  sand. 
Then  direct  a  stream  of  water  into  the  sand  (as  by  inserting  end 
of  garden-hose  nearly  to  bottom  of  crock),  allowing  water  to 
overflow  at  top  of  crock;  continue  this  washing  (with  violent 
agitation  of  the  sand)  until  the  overflow  is  free  from  sediment. 
Decant,  refill  crock  with  distilled  water,  stir  sand  vigorously,  and 
decant  again.  Refill  with  distilled  water,  stir  and  decant  once 
more.  After  second  decanting  of  distilled  water,  spread  sand 
on  clean  paper  and  allow  it  to  become  air-dry,  avoiding  dust  or 
other  foreign  matter. 

Prepai^ation  of  Crocks.  For  culture  pots,  cylindrical  half- 
gallon  stoneware  crocks  (glazed  within  and  without,  but  not 
dark-colored  externally)  about  14  cm.  high  and  14  cm.  in  diam- 
eter, are  to  be  used.  For  definite  reference,  they  should  be 
serially  numbered  with  paint,  and  solution  designations  may  be 
marked  on  them  with  wax  pencil. 

Twenty-five  hundred  grams  of  air-dry  washed  sand  is  to  be 
used  for  each  crock,  which  should  fill  it  to  within  about  two  centi- 

47 


meters  from  the  top.  A  glass  suction  tube  (with  inside  diameter 
about  4  mm.,  is  to  be  placed  vertically  against  the  wall  of  the 
crock,  its  lower  end  resting  on  bottom  of  crock  and  its  upper  end 
extending  about  1  cm.  above  the  rim.  This  tube  is  to  be  placed 
before  sand  is  poured  into  crock  and  will  be  held  in  position  by 
the  sand.  The  lower  end  of  the  tube  is  to  be  loosely  plugged  with 
glass-wool  and  tufts  of  the  wool  are  to  extend  one  or  two  centi- 
meters beyond  the  tube,  so  that  sand  may  rest  on  these  and  thus 
hold  the  plug  in  place. 

A  supply  orifice  is  furnished  by  a  paraffined  paper  cone  (or  a 
100-cc.  wide-mouth  bottle  with  the  bottom  removed) ,  standing 
at  the  center  of  the  sand  surface  and  embedded  in  it  to  a  depth 
of  about  two  centimeters.  The  paper  cone  should  be  about  six 
centimeters  high,  four  centimeters  in  diameter  at  its  larger 
(lower)  end  and  two  centimeters  in  diameter  at  its  smaller 
(upper)  end.  These  cones  are  rolled  from  heavy  paper,  fastened 
by  a  pin  or  paper-clip,  and  are  heavily  paraffined. 

Record  the  total  weight  of  crock,  tube,  cone  and  sand.  Cone 
is  not  permanently  placed  till  after  seedlings  are  in  position. 

The  Seedlings.  The  seeds  are  to  be  soaked  in  germination 
solution  and  allowed  to  germinate  on  the  germination  net,  just 
*  as  for  water-cultures,  the  shoots  being  four  centimeters  high 
when  transplanting  occurs.  Selection  is  made  just  as  for  water- 
cultures.  It  is  of  course  desirable  that  all  seedlings  be  as  nearly 
alike  as  possible. 

Introduction  of  Seedlings.  When  seedlings  are  ready,  some 
nutrient  solution  is  poured  on  to  the  sand,  to  moisten  it  (a  liter 
of  solution  should  be  ready,  but  only  a  little  is  used  at  the  start) , 
the  surface  is  levelled  and  the  selected  seedlings  are  introduced, 
five  in  each  crock.  These  are  to  be  selected  beforehand,  as  in  the 
case  of  water-cultures.  They  are  planted  so  that  the  grains  will 
lie  about  one-half  centimeter  below  the  sand  surface,  equally 
spaced,  in  a  circle  half-way  between  the  supply  cone  and  the  wall 
of  the  crock.  A  flat  wooden  dibble  (like  a  spatula)  about  fifteen 
millimeters  wide  and  having  a  sharp  edge  is  convenient  for  set- 
ting the  seedlings.  (An  ordinary  pot  label  with  broad  end 
thinned  serves  will.)  Care  should  be  exercised  not  to  injure  the 
roots. 

The  supply  cone  is  introduced  in  the  center  of  the  sand  sur- 
face after  the  seedlings  are  in  place,  its  larger  end  downward 
and  embedded  in  the  sand  to  a  depth  of  about  two  centimeters. 
Then  nutrient  solution  is  poured  in  through  the  cone  until  the 
liquid  surface  is  about  one  centimeter  above  the  sand,  and  the 

48 


crock  is  slightly  jarred  to  settle  the  sand  about  the  roots  of  the 
plants  and  to  give  a  flat  surface  for  the  wax  seal. 

An  aspirator  is  now  connected  to  the  suction  tube  and  the 
excess  of  solution  is  drawn  off  until  the  moisture  content  of  the 
sand  is  reduced  to  about  sixteen  per  cent,  (dry-weight  basis). 
The  sand  is  then  flooded  a  second  time  with  nutrient  solution,  and 
the  excess  is  again  removed,  as  just  described.  The  aspirator 
tube  should  be  joined  to  the  culture  tube  with  a  suitable  bottle 
intervening  as  a  trap  to  catch  the  solution  that  is  removed.  This 
bottle  is  to  be  marked  so  as  to  indicate  when  the  desired  volume 
of  solution  has  been  removed,  a  device  that  will  save  many 
weighings  if  the  volume  of  solution  added  is  known.  The  weight 
of  the  seedlings  may  be  neglected  and  the  required  moisture 
content  of  the  sand  may  have  any  value  between  fifteen  and  sev- 
enteen per  cent,  (dry- weight  basis). 

The  Wax  Seal.  To  hinder  evaporation  from  the  soil,  the  free 
sand  surface  is  sealed  with  a  mixture  of  eighty  parts  (by  weight) 
of  "Parawax"  and  twenty  parts  of  "Vaseline,  White"  (Ches- 
brough  brand).  Have  the  mixture  only  warm  enough  to  flow 
freely,  otherwise  the  plants  may  be  injured  where  their  stems 
are  in  contact  with  the  seal.  Pour  the  wax  over  the  sand  sur- 
face, so  as  to  form  a  layer  from  two  to  four  millimeters  thick, 
being  sure  that  the  wax  forms  a  tight  joint  at  its  junction  with 
the  crock  wall  and  with  the  supply  cone,  also  that  it  makes  good 
contact  with  the  seedling  shoots.  (On  wax  seals,  see :  Briggs  and 
Shantz,  Bot.  Gaz.  51:  210-219.     1911.) 

Manipulations  During  the  Culture  Period.  At  the  end  of  each 
314-day  period  each  culture  is  weighed,  and  suflficient  distilled 
water  is  added  (through  the  cone)  to  bring  the  sand  moisture 
content  back  to  the  original  sixteen  per  cent,,  and  record  is 
kept  of  the  amount  of  water  needed.  Then  the  excess  liquid  is 
removed  (aspirator)  until  the  moisture  content  is  about  ten  per 
cent.  Then  the  sand  is  again  flooded  with  fresh  solution  and  the 
excess  is  once  more  removed,  this  time  leaving  the  moisture  con- 
tent at  sixteen  per  cent.  The  culture  is  then  ready  for  the  suc- 
ceeding 31/^-day  period. 

From  the  records  showing  the  amounts  of  distilled  water 
added  to  any  culture  are  to  be  obtained  data  of  transpirational 
water  loss.  It  will  be  seen  that  the  amount  of  salt  absorbed  by 
the  plants  is  neglected  (as  though  the  plants  absorbed  only  water 
from  the  solution),  but  the  error  thus  introduced  will  be  more 
truly  negligible  than  the  one  that  would  be  encountered  if 
nutrient  solution  were  used  in  place  of  distilled  water. 

49 


Growth  Phases.  These  are  the  same  as  for  water-cultures 
with  wheat.  For  the  reproductive  phase  the  plants  will  require 
mechanical  support.  (See  McCall,  Jour.  Amer.  Soc.  Agron.  10: 
127-134.     1918.) 

Location,  Exposure,  Climatic  Records,  etc.  These  are  all  the 
same  as  for  water-cultures  with  wheat. 

The  Plant  Records.  These  are  the  same  as  for  water-cultures, 
excepting  that  the  root  weights  require  special  manipulation. 
The  wax  seal  is  removed  and  the  contents  of  the  crock  are  placed 
on  a  wire  sieve  (about  ten  meshes  to  the  inch) ,  through  which 
the  free  sand  is  washed  with  a  stream  of  water.  Then  the  roots 
are  severed  from  the  tops,  as  in  the  case  of  water-cultures,  and 
the  tops  are  treated  as  before  described.  The  root  systems  of 
all  plants  from  the  same  crock  (including  the  adhering  sand) 
are  then  brought  together,  dried  at  102°  C,  and  the  dry  weight 
for  each  culture  is  determined.  Then  each  mass  of  roots  is 
ignited  in  a  weighed  porcelain  crucible  till  all  organic  matter  has 
been  removed,  the  weight  of  the  remaining  mineral  matter  is 
determined,  and  this  value  is  subtracted  from  the  original  dry 
weight  of  roots  and  sand,  to  give  approximately  the  dry  weight 
of  the  roots  alone.  The  errors  introduced  by  this  method  are 
negligible  in  this  sort  of  work.  (See  McCall,  Soil  Science  2: 
223.     1916.) 

CULTURES  WITH  SOY  BEAN. 

Experimenters  who  wish  to  work  with  soy  bean  are  requested 
to  communicate  immediately  with  the  committee.  While  the 
general  procedure  for  this  plant  will  be  similar  to  that  for  wheat, 
yet  some  details  must  necessarily  be  different,  and  many  of  these 
are  not  yet  worked  out  by  preliminary  experimentation. 

THE  SUB-DIVISION  OF  THE  PROJECT. 

Introduction. — The  following  notes  may  serve  as  suggestions, 
to  aid  cooperators  in  choosing  their  problems  in  the  project.  It 
is  hoped  that  cooperators  will  choose  for  their  work  those  por- 
tio^is  of  the  plan  in  which  they  feel  most  interested.  At  the  same 
time,  the  committee  will  be  glad  to  aid  in  this  connection,  and  it 
may  be  necessary  (in  order  that  all  parts  of  the  plan  may  receive 
attention)  for  the  committee  to  make  special  requests  at  a  some- 
what later  time. 

In  the  first  place,  it  is  strongly  urged  that  every  experiment 
include  at  least  three  cultures  with  Shive's  best  solution  for  the 

50 


early  growth  of  wheat,  the  solution  called  control  in  the  preced- 
ing pages.  It  is  largely  through  these  controls  that  climatic 
conditions  and  different  groups  of  solutions  tested  at  different 
times  and  places  are  to  be  compared.  At  a  later  time  it  may  be- 
come expedient  to  adopt  some  other  solution  as  general  control, 
but  the  one  mentioned  is  the  logical  one  to  use  in  the  early  stages 
of  our  studies. 

The  following  paragraphs  aim  to  present  some  of  the  most 
promising  ways  of  grouping  the  one  hundred  and  twenty-three 
solutions  that  are  first  to  be  tested  (osmotic  value,  1.00  atm.). 

Suhdivision  by  Types.  Each  set  of  21  (or  19  or  20)  solu- 
tions (tables  I-VI)  furnishes  a  logical  group  for  experimen- 
tation. Such  a  group  includes  (with  the  triplicate  control)  22, 
23  or  24  cultures,  which  is  a  convenient  number  for  an  experi- 
menter who  does  not  devote  nearly  all  his  time  to  the  work.  It 
may  be  noted  that  types  V  and  VI  involve  some  physical-chemical 
difficulties  not  encountered  with  the  others,  and  those  who  have 
had  experience  with  this  sort  of  difficulty  are  urged  to  undertake 
the  study  of  these  two  exceptional  types.  Type  I  is  the  one  on 
which  most  of  the  earlier  work  has  been  done. 

Of  course  it  will  be  desirable,  where  possible,  to  carry  out 
each  experiment  with  these  type  groups  in  duplicate,  triplicate, 
etc.,  and  an  experimenter  may  thus  give  his  entire  time  to  the 
solutions  of  a  single  group. 

It  will  also  be  desirable,  especially  where  two  or  more  experi- 
menters can  work  together,  that  the  full  sets  of  several  solution 
types  (or  even  all  six  of  them)  be  tested  simultaneously,  in  which 
case  a  single  triplicate  control  will  serve  for  all  sets. 

Suhdivision  Into  Groups  Smaller  Than  Type  Groups.  For 
smaller  groups  than  are  represented  by  the  six  different  types  of 
solution,  any  solutions  may  be  selected,  either  merely  at  random, 
or  because  of  a  personal  interest.  It  will  be  especially  desirable 
to  study  and  compare  in  this  way  just  those  solutions  that  have 
already  given  good  promise.  For  the  seedling  phase  of  growth 
Shive's  (1915)  results  and  those  of  Livingston  and  Tottingham 
(1918)  are  of  special  interest  as  indicating  promising  solutions. 
A  study  of  Shive's  graphic  summary  (page  390)  for  his  optimal 
concentration  will  suggest  small  groups  of  solutions  of  type  I 
that  may  be  profitably  compared.  Table  2  of  Livingston  and 
Tottingham  may  furnish  similar  suggestions  for  type  III.  Many 
other  sources  of  similar  suggestions  will  doubtless  become  avail- 
able as  soon  as  a  few  experiments  has  been  carried  out,  and  such 


51 


suggestions  may  already  exist  in  unpublished'  or  published 
records. 

It  is  not  necessary  that  the  plan  of  subdividing  by  solution 
types  should  necessarily  involve  the  testing  of  all  the  solutions 
of  a  given  type  at  once.  The  solutions  may  be  graphed  on  the 
triangular  diagram  and  then  the  diagram  may  be  arbitrarily 
divided  into  two  or  more  regions,  each  region  being  considered 
separately.  Thus,  the  first  ten  or  eleven  solutions  of  any  one 
of  the  tables  as  here  given  may  be  considered  as  a  first  group, 
the  remaining  solutions  of  that  type  constituting  a  second  group, 
to  be  tested  after  the  first. 

An  experimental  comparison  of  the  physiological  properties 
of  any  single  solution  given  in  tables  I  to  VI,  with  the  control 
solution,  will  constitute  a  valuable  step  toward  the  working  out 
of  the  plan.  It  is  hoped  that  many  workers  who  are  not  able  to 
devote  a  great  deal  of  time  to  this  project  will  nevertheless  join 
in  the  work,  even  by  testing  a  single  solution.  Indeed,  the  study 
of  the  relation  of  climatic  conditions  to  growth  may  be  greatly 
advanced  if  a  large  number  of  experimenters  will  carry  out  cul- 
tures with  the  control  solution  alone.  If  one  could  do  no  more, 
it  would  be  well  worth  while  to  get  the  plant  measurements  for  a 
number  of  control  cultures,  at  any  time  during  the  year,  of  course 
obtaining  at  the  same  time  the  climatic  data  mentioned  in  the 
plan.  The  growth  of  wheat  in  Shive's  best  solution  for  this  plant 
might  thus  become  a  sort  of  common  criterion  by  which  different 
climatic  complexes  (for  different  seasons  and  for  different  sta- 
tions) might  be  compared,  in  terms  of  their  influence  on  the 
physiological  processes  of  wheat. 

As  the  work  goes  forward  the  committee  will  furnish  further 
suggestions  as  to  the  subdivision  of  the  plan,  upon  request. 

REPORTS    OF    RESULTS. 

As  has  been  said,  all  cooperators  are  strongly  urged  to  send 
to  the  committee  all  results  obtained  just  as  promptly  as  possible. 
Forms  for  such  reports  will  be  supplied  to  cooperators  on 
request. 

SUSCEPTIBILITY  TO  ATTACK  BY  BACTERIA  OR  FUNGI. 

Emphasis  has  been  recently  placed  on  the  observed  fact  that 
a  poorly  balanced  fertilizer  treatment  may  not  only  produce 
smaller  or  less  well-developed  plants  than  does  a  more  nearly 
perfect  treatment,  but  such  poor  treatment  may  frequently  also 

52 


produce  plants  of  apparently  satisfactory  appearance,  which 
nevertheless  are  very  unsatisfactory  on  account  of  a  high  degree 
of  susceptibility  to  injurious  attacks  by  parasitic  organisms. 
Plant  pathologists  agree  that  the  problem  thus  suggested  is  of 
very  great  fundamental  importance  and  that  definite' information 
in  this  general  connection  should  be  made  available  as  rapidly 
as  possible.  It  is  seen  that  this  problem  involves  both  pathology 
and  physiology.  Susceptibility  to  the  attacks  of  a  certain  para- 
sitic fungus  or  bacterial  form  may  be  considered  as  one  of  the 
physiological  characters  that  need  to  be  understood  for  agricul- 
tural plants,  and  it  is  especially  important  that  the  relations  be- 
tween such  susceptibility  and  the  salt  treatment  of  the  plants  in 
question  should  receive  attention. 

It  is  consequently  planned  that  cooperators  in  the  present 
project  who  are  familiar  with  the  experimental  methods  of  plant 
pathology  may  undertake  experimentation  in  this  field.  Of 
course  such  experimentation  must  needs  deal  with  the  plants 
employed  for  the  simply  nutritional  aspect  of  our  problem;  for 
the  beginning,  with  "Marquis"  wheat  and  soy  bean. 

It  is  planned  that  suitable  groups  of  solutions  may  be  em- 
ployed in  either  water-culture  or  sand-culture  and  that  when 
the  plants  have  reached  a  proper  stage  of  development  they  may 
be  all  tested  for  different  degrees  of  susceptibility  by  being  simi- 
larly inoculated  with  the  fungus  or  bacterium.  The  final  records 
in  this  sort  of  study  will  of  course  deal  with  the  relative  amounts 
of  infection  and  with  the  relative  degrees  of  injury  produced  by 
infection. 

In  order  that  the  results  may  be  standardized,  it  is  necessary 
that  the  plants  be  grown  according  to  the  details  of  the  foregoing 
plan  for  work  on  salt  nutrition  itself,  and  it  is  practically  neces- 
sary that  these  inoculation  experiments  include  uninoculated  con- 
trols having  the  same  solution  treatments  as  are  given  to  the 
inoculated  cultures.  The  uninoculated  cultures  will  then  furnish 
the  regular  plant  measurement  (of  the  foregoing  plan),  with 
which  similar  data  from  the  inoculated  cultures  are  to  be  com- 
pared. For  an  illustration,  a  duplicate  water-culture  series  with 
solutions  of  type  I  may  be  carried  out  until  the  end  of  the  third 
week  of  the  seedling  phase  of  wheat.  At  that  time  the  visual 
observations  on  the  plants  are  to  be  made  with  special  care,  after 
which  one  culture  with  each  solution  is  to  be  inoculated  and  the 
cultures  are  to  be  continued  to  the  end  of  the  five-week  period  of 
this  phase.  Final  observations  and  measurements  are  to  be  made 
on  all  cultures.  It  is  very  essential  that  special  attention  be  given 

53 


to  the  climatic  conditions  at  the  time  of  inoculation  and  later ;  it 
may  be  desirable  to  read  the  atmometers  daily  or  even  more  fre- 
quently, and  to  obtain  thermograph  tracings  of  the  temperature 
and  special  notes  on  the  degree  of  cloudiness.  The  committee 
will  be  glad  to  discuss  forms  of  experiment  in  this  field  with  any 
cooperator  who  is  interested.  The  details  of  such  experiments 
need  to  be  worked  out  for  each  special  case. 

CHEMICAL  COMPOSITION  OF  THE  PLANTS  AS  RELATED 

TO    THE    CHARACTERISTICS    OF    THE 

CULTURE  MEDIUM. 

Besides  the  plant  records  mentioned  in  the  preceding  pages, 
it  is  planned  that  the  plants  of  selected  cultures  may  be  sub- 
jected to  chemical  analysis,  to  determine  the  proportions  of  some 
of  their  constituents,  and  that  the  results  of  these  analyses  may 
be  correlated  with  the  characteristics  of  the  media  in  which  the 
plants  have  been  grown.  Those  who  so  desire  may  take  part  in 
this  aspect  of  the  project  by  communicating  with  the  com- 
mittee, which  will  attempt  to  make  arrangements  by  which  one 
cooperator  may  grow  the  plants  while  another  performs  the 
analyses.  These  analyses  are  planned  to  deal  with  both  mineral 
and  organic  constituents  of  the  plants. 


^ 


54 


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Makers 

Syracuse,  N. Y. 

PAT.  JAN.  21,1908 


'■^^son 


UNIVERSITY  OF  CAUFORNIA  UBRARV 


